Electrochromic rearview mirror element incorporating a third surface reflector

ABSTRACT

The inventive electrochromic mirror may be used in a vehicle rearview mirror assembly having a light source positioned behind the electrochromic mirror for selectively projecting light through the mirror. The electrochromic mirror includes front and rear spaced elements each having front and rear surfaces and being sealably bonded together in a spaced-apart relationship to define a chamber, a layer of transparent conductive material disposed on the rear surface of the front element, an electrochromic material is contained within the chamber, and a second electrode overlies the front surface of the rear element in contact with the electrochromic material. The second electrode includes a layer of reflective material and a partially transmissive coating of and is disposed over substantially all of the front surface of the rear element. The second electrode further includes a region in front of the light source that is at least partially transmissive.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of U.S. patent applicationSer. No. 09/994,218, filed on Nov. 26, 2001, entitled “ELECTROCHROMICREARVIEW MIRROR INCORPORATING A THIRD SURFACE PARTIALLY TRANSMISSIVEREFLECTOR,” by William L. Tonar et al.; which is a continuation of U.S.patent application Ser. No. 09/311,955, filed on May 14, 1999, entitled“ELECTROCHROMIC REARVIEW MIRROR INCORPORATING A THIRD SURFACE METALREFLECTOR AND A DISPLAY/SIGNAL LIGHT,” by William L. Tonar et al., nowU.S. Pat. No. 6,356,376; which is a continuation-in-part of co-pendingU.S. patent application Ser. No. 09/206,788, filed on Dec. 7, 1998,entitled “ELECTROCHROMIC REARVIEW MIRROR INCORPORATING A THIRD SURFACEMETAL REFLECTOR AND A DISPLAY/SIGNAL LIGHT,” by William L. Tonar et al.,now U.S. Pat. No. 6,166,848; which is a continuation-in-part ofco-pending U.S. patent application Ser. No. 09/197,400, filed on Nov.20, 1998, entitled “ELECTROCHROMIC REARVIEW MIRROR INCORPORATING A THIRDSURFACE METAL REFLECTOR AND A DISPLAY/SIGNAL LIGHT,” by William L. Tonaret al., now U.S. Pat. No. 6,111,684; which is a continuation-in-part ofco-pending U.S. patent application Ser. No. 09/114,386, filed on Jul.13, 1998, entitled “ELECTROCHROMIC REARVIEW MIRROR INCORPORATING A THIRDSURFACE METAL REFLECTOR,” by Jeffrey A. Forgette et al., now U.S. Pat.No. 6,064,508; which is a continuation of U.S. patent application Ser.No. 08/832,587, filed on Apr. 2, 1997, entitled “ELECTROCHROMIC REARVIEWMIRROR INCORPORATING A THIRD SURFACE METAL REFLECTOR,” by Jeffrey A.Forgette et al., now U.S. Pat. No. 5,818,625, the entire disclosures ofwhich are herein incorporated by reference.

[0002] U.S. Pat. No. 6,166,848 is also a continuation-in-part of U.S.patent application Ser. No. 09/175,984 filed on Oct. 20, 1998, entitled“ELECTROCHROMIC MIRRORS HAVING A SIGNAL LIGHT,” by Jeffrey A. Forgetteet al., now U.S. Pat. No. 6,111,683, which is a continuation-in-part ofU.S. patent application Ser. No. 08/831,808, entitled “AN INFORMATIONDISPLAY AREA ON ELECTROCHROMIC MIRRORS HAVING A THIRD SURFACE METALREFLECTOR,” filed on Apr. 2, 1997, by Jeffrey A. Forgette et al., nowU.S. Pat. No. 5,825,527, the entire disclosures of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

[0003] This invention relates to electrochromic rearview mirrors formotor vehicles and, more particularly, to improved electrochromicrearview mirrors incorporating a third surface reflector/electrode incontact with at least one solution-phase electrochromic material.

[0004] Heretofore, various rearview mirrors for motor vehicles have beenproposed which change from the full reflectance mode (day) to thepartial reflectance mode(s) (night) for glare-protection purposes fromlight emanating from the headlights of vehicles approaching from therear. Among such devices are those wherein the transmittance is variedby thermochromic, photochromic, or electro-optic means (e.g., liquidcrystal, dipolar suspension, electrophoretic, electrochromic, etc.) andwhere the variable transmittance characteristic affects electromagneticradiation that is at least partly in the visible spectrum (wavelengthsfrom about 3800 Å to about 7800 Å). Devices of reversibly variabletransmittance to electromagnetic radiation have been proposed as thevariable transmittance element in variable transmittance light-filters,variable reflectance mirrors, and display devices, which employ suchlight-filters or mirrors in conveying information. These variabletransmittance light filters have included windows.

[0005] Devices of reversibly variable transmittance to electromagneticradiation, wherein the transmittance is altered by electrochromic means,are described, for example, by Chang, “Electrochromic andElectrochemichromic Materials and Phenomena,” in Non-emissiveElectrooptic Displays, A. Kmetz and K. von Willisen, eds. Plenum Press,New York, N.Y. 1976, pp. 155-196 (1976) and in various parts ofElectrochromism, P. M. S. Monk, R. J. Mortimer, D. R. Rosseinsky, VCHPublishers, Inc., New York, N.Y. (1995). Numerous electrochromic devicesare known in the art. See, e.g., Manos, U.S. Pat. No. 3,451,741;Bredfeldt et al., U.S. Pat. No. 4,090,358; Clecak et al., U.S. Pat. No.4,139,276; Kissa et al., U.S. Pat. No. 3,453,038; Rogers, U.S. Pat. Nos.3,652,149, 3,774,988 and 3,873,185; and Jones et al., U.S. Pat. Nos.3,282,157, 3,282,158, 3,282,160 and 3,283,656.

[0006] In addition to these devices, there are commercially availableelectrochromic devices and associated circuitry, such as those disclosedin U.S. Pat. No. 4,902,108, entitled “SINGLE-COMPARTMENT, SELF-ERASING,SOLUTION-PHASE ELECTROCHROMIC DEVICES SOLUTIONS FOR USE THEREIN, ANDUSES THEREOF,” issued Feb. 20, 1990, to H.J. Byker; Canadian Pat. No.1,300,945, entitled “AUTOMATIC REARVIEW MIRROR SYSTEM FOR AUTOMOTIVEVEHICLES,” issued May 19, 1992, to J. H. Bechtel et al.; U.S. Pat. No.5,128,799, entitled “VARIABLE REFLECTANCE MOTOR VEHICLE MIRROR,” issuedJul. 7, 1992, to H. J. Byker; U.S. Pat. No. 5,202,787, entitled“ELECTRO-OPTIC DEVICE,” issued Apr. 13, 1993, to H. J. Byker et al.;U.S. Pat. No. 5,204,778, entitled “CONTROL SYSTEM FOR AUTOMATIC REARVIEWMIRRORS,” issued Apr. 20, 1993, to J. H. Bechtel; U.S. Pat. No.5,278,693, entitled “TINTED SOLUTION-PHASE ELECTROCHROMIC MIRRORS,”issued Jan. 11, 1994, to D. A. Theiste et al.; U.S. Pat. No. 5,280,380,entitled “UV-STABILIZED COMPOSITIONS AND METHODS,” issued Jan. 18, 1994,to H. J. Byker; U.S. Pat. No. 5,282,077, entitled “VARIABLE REFLECTANCEMIRROR,” issued Jan. 25, 1994, to H.J. Byker; U.S. Pat. No. 5,294,376,entitled “BIPYRIDINIUM SALT SOLUTIONS,” issued Mar. 15, 1994, to H.J.Byker; U.S. Pat. No. 5,336,448, entitled “ELECTROCHROMIC DEVICES WITHBIPYRIDINIUM SALT SOLUTIONS,” issued Aug. 9, 1994, to H.J. Byker; U.S.Pat. No. 5,434,407, entitled “AUTOMATIC REARVIEW MIRROR INCORPORATINGLIGHT PIPE,” issued Jan. 18, 1995, to F. T. Bauer et al.; U.S. Pat. No.5,448,397, entitled “OUTSIDE AUTOMATIC REARVIEW MIRROR FOR AUTOMOTIVEVEHICLES,” issued Sep. 5, 1995, to W.L. Tonar; and U.S. Pat. No.5,451,822, entitled “ELECTRONIC CONTROL SYSTEM,” issued Sep. 19, 1995,to J. H. Bechtel et al. Each of these patents is commonly assigned withthe present invention and the disclosures of each, including thereferences contained therein, are hereby incorporated herein in theirentirety by reference. Such electrochromic devices may be utilized in afully integrated inside/outside rearview mirror system or as separateinside or outside rearview mirror systems.

[0007]FIG. 1 shows a typical electrochromic mirror device 10, havingfront and rear planar elements 12 and 16, respectively. A transparentconductive coating 14 is placed on the rear face of the front element12, and another transparent conductive coating 18 is placed on the frontface of rear element 16. A reflector (20 a, 20 b and 20 c), typicallycomprising a silver metal layer 20 a covered by a protective coppermetal layer 20 b, and one or more layers of protective paint 20 c, isdisposed on the rear face of the rear element 16. For clarity ofdescription of such a structure, the front surface of the front glasselement is sometimes referred to as the first surface, and the insidesurface of the front glass element is sometimes referred to as thesecond surface. The inside surface of the rear glass element issometimes referred to as the third surface, and the back surface of therear glass element is sometimes referred to as the fourth surface. Thefront and rear elements are held in a parallel and spaced-apartrelationship by seal 22, thereby creating a chamber 26. Theelectrochromic medium 24 is contained in space 26. The electrochromicmedium 24 is in direct contact with transparent electrode layers 14 and18, through which passes electromagnetic radiation whose intensity isreversibly modulated in the device by a variable voltage or potentialapplied to electrode layers 14 and 18 through clip contacts and anelectronic circuit (not shown).

[0008] The electrochromic medium 24 placed in space 26 may includesurface-confined, electrode position-type or solution-phase-typeelectrochromic materials and combinations thereof. In an allsolution-phase medium, the electrochemical properties of the solvent,optional inert electrolyte, anodic materials, cathodic materials, andany other components that might be present in the solution arepreferably such that no significant electrochemical or other changesoccur at a potential difference which oxidizes anodic material andreduces the cathodic material other than the electrochemical oxidationof the anodic material, electrochemical reduction of the cathodicmaterial, and the self-erasing reaction between the oxidized form of theanodic material and the reduced form of the cathodic material.

[0009] In most cases, when there is no electrical potential differencebetween transparent conductors 14 and 18, the electrochromic medium 24in space 26 is essentially colorless or nearly colorless, and incominglight (I_(o)) enters through front element 12, passes throughtransparent coating 14, electrochromic containing chamber 26,transparent coating 18, rear element 16, and reflects off layer 20 a andtravels back through the device and out front element 12. Typically, themagnitude of the reflected image (I_(R)) with no electrical potentialdifference is about 45 percent to about 85 percent of the incident lightintensity (I_(o)). The exact value depends on many variables outlinedbelow, such as, for example, the residual reflection (I′_(R)) from thefront face of the front element, as well as secondary reflections fromthe interfaces between: the front element 12 and the front transparentelectrode 14, the front transparent electrode 14 and the electrochromicmedium 24, the electrochromic medium 24 and the second transparentelectrode 18, and the second transparent electrode 18 and the rearelement 16. These reflections are well known in the art and are due tothe difference in refractive indices between one material and another asthe light crosses the interface between the two. If the front elementand the back element are not parallel, then the residual reflectance(I′_(R)) or other secondary reflections will not superimpose with thereflected image (I_(R)) from mirror surface 20 a, and a double imagewill appear (where an observer would see what appears to be double (ortriple) the number of objects actually present in the reflected image).

[0010] There are minimum requirements for the magnitude of the reflectedimage depending on whether the electrochromic mirrors are placed on theinside or the outside of the vehicle. For example, according to currentrequirements from most automobile manufacturers, inside mirrorspreferably have a high end reflectivity of at least 70 percent, andoutside mirrors must have a high end reflectivity of at least 35percent.

[0011] Electrode layers 14 and 18 are connected to electronic circuitrywhich is effective to electrically energize the electrochromic medium,such that when a potential is applied across the transparent conductors14 and 18, electrochromic medium in space 26 darkens, such that incidentlight (I_(o)) is attenuated as the light passes toward the reflector 20a and as it passes back through after being reflected. By adjusting thepotential difference between the transparent electrodes, such a devicecan function as a “gray-scale” device, with continuously variabletransmittance over a wide range. For solution-phase electrochromicsystems, when the potential between the electrodes is removed orreturned to zero, the device spontaneously returns to the same,zero-potential, equilibrium color and transmittance as the device hadbefore the potential was applied. Other electrochromic materials areavailable for making electrochromic devices. For example, theelectrochromic medium may include electrochromic materials that aresolid metal oxides, redox active polymers, and hybrid combinations ofsolution-phase and solid metal oxides or redox active polymers; however,the above-described solution-phase design is typical of most of theelectrochromic devices presently in use.

[0012] Even before a fourth surface reflector electrochromic mirror wascommercially available, various groups researching electrochromicdevices had discussed moving the reflector from the fourth surface tothe third surface. Such a design has advantages in that it should,theoretically, be easier to manufacture because there are fewer layersto build into a device, i.e., the third surface transparent electrode isnot necessary when there is a third surface reflector/electrode.Although this concept was described as early as 1966, no group hadcommercial success because of the exacting criteria demanded from aworkable auto-dimming mirror incorporating a third surface reflector.U.S. Pat. No. 3,280,701, entitled “OPTICALLY VARIABLE ONE-WAY MIRROR,”issued Oct. 25, 1966, to J. F. Donnelly et al. has one of the earliestdiscussions of a third surface reflector for a system using a pH-inducedcolor change to attenuate light.

[0013] U.S. Pat. No. 5,066,112, entitled “PERIMETER COATED,ELECTRO-OPTIC MIRROR,” issued Nov. 19, 1991, to N. R. Lynam et al.,teaches an electro-optic mirror with a conductive coating applied to theperimeter of the front and rear glass elements for concealing the seal.Although a third surface reflector is discussed therein, the materialslisted as being useful as a third surface reflector suffer from one ormore of the following deficiencies: not having sufficient reflectivityfor use as an inside mirror, or not being stable when in contact with asolution-phase electrochromic medium containing at least onesolution-phase electrochromic material.

[0014] Others have broached the topic of a reflector/electrode disposedin the middle of an all solid state-type device. For example, U.S. Pat.Nos. 4,762,401, 4,973,141, and 5,069,535 to Baucke et al. teach anelectrochromic mirror having the following structure: a glass element, atransparent (ITO) electrode, a tungsten oxide electrochromic layer, asolid ion conducting layer, a single layer hydrogen ion-permeablereflector, a solid ion conducting layer, a hydrogen ion storage layer, acatalytic layer, a rear metallic layer, and a back element (representingthe conventional third and fourth surface). The reflector is notdeposited on the third surface and is not directly in contact withelectrochromic materials, certainly not at least one solution-phaseelectrochromic material and associated medium. Consequently, it isdesirable to provide an improved high reflectivity electrochromicrearview mirror having a third surface reflector/electrode in contactwith a solution-phase electrochromic medium containing at least oneelectrochromic material.

[0015] In the past, information, images or symbols from displays, suchas vacuum fluorescent displays, have been displayed on electrochromicrearview mirrors for motor vehicles with reflective layers on the fourthsurface of the mirror. The display is visible to the vehicle occupant byremoving all of the reflective layer on a portion of the fourth surfaceand placing the display in that area. Although this design worksadequately due to the transparent conductors on the second and thirdsurface to impart current to the electrochromic medium, presently nodesign is commercially available which allows a display device to beincorporated into a mirror that has a reflective layer on the thirdsurface. Removing all of the reflective layer on the third surface inthe area aligned with the display area or the glare sensor area causessevere residual color problems when the electrochromic medium darkensand clears because, although colorization occurs at the transparentelectrode on the second surface, there is no corresponding electrode onthe third surface in that corresponding area to balance the charge. As aresult, the color generated at the second surface (across from thedisplay area or the glare sensor area) will not darken or clear at thesame rate as other areas with balanced electrodes. This color variationis significant and is very aesthetically unappealing to the vehicleoccupants.

[0016] Similar problems exist for outside rearview mirror assembliesthat include signal lights, such as turn signal lights, behind the rearsurface of the mirror. Examples of such signal mirrors are disclosed inU.S. Pat. Nos. 5,207,492, 5,361,190, and 5,788,357. By providing a turnsignal light in an outside mirror assembly, a vehicle, or other vehiclestravelling in the blind spot of the subject vehicle, will be more likelyto notice when the driver has activated the vehicle's turn signal andthereby attempt to avoid an accident. Such mirror assemblies typicallyemploy a dichroic mirror and a plurality of red LEDs mounted behind themirror as the signal light source. The dichroic mirror includes a glasssubstrate and a dichroic reflective coating provided on the rear surfaceof the glass plate that transmits the red light generated by the LEDs aswell as infrared radiation while reflecting all light and radiationhaving wavelengths less than that of red light. By utilizing a dichroicmirror, such mirror assemblies hide the LEDs when not in use to providethe general appearance of a typical rearview mirror, and allow the redlight from such LEDs to pass through the dichroic mirror and be visibleto drivers of vehicles behind and to the side of the vehicle in whichsuch a mirror assembly is mounted. Examples of such signal mirrors aredisclosed in U.S. Pat. Nos. 5,361,190 and 5,788,357.

[0017] In daylight, the intensity of the LEDs must be relatively high toenable those in other vehicles to readily notice the signal lights.Because the image reflected toward the driver is also relatively high indaylight, the brightness of the LEDs is not overly distracting. However,at night the same LED intensity could be very distracting, and hence,potentially hazardous. To avoid this problem, a day/night sensingcircuit is mounted in the signal light subassembly behind the dichroicmirror to sense whether it is daytime or nighttime and toggle theintensity of the LEDs between two different intensity levels. The sensoremployed in the day/night sensing circuit is most sensitive to red andinfrared light so as to more easily distinguish between daylightconditions and the bright glare from the headlights of a vehicleapproaching from the rear. Hence, the sensor may be mounted behind thedichroic coating on the dichroic mirror.

[0018] The dichroic mirrors used in the above-described outside mirrorassemblies suffer from the same problems of many outside mirrorassemblies in that their reflectance cannot be dynamically varied toreduce nighttime glare from the headlights of other vehicles.

[0019] Although outside mirror assemblies exist that include signallights and other outside mirror assemblies exist that includeelectrochromic mirrors, signal lights have not been provided in mirrorassemblies having an electrochromic mirror because the dichroic coatingneeded to hide the LEDs of the signal light typically cannot be appliedto an electrochromic mirror, particularly those mirrors that employ athird surface reflector/electrode.

SUMMARY OF THE INVENTION

[0020] Accordingly, it is an aspect of the present invention to solvethe above problems by providing an electrochromic rearview mirrorassembly that includes a third surface reflector/electrode that providesa continuous layer of electrically conductive material across the entirevisible surface of the rear element of the mirror, even those regionsthat lie in front of a light source, such as a signal light, informationdisplay, or illuminator, or a light sensor or receptor, that ispositioned behind the electrochromic mirror. Yet another aspect of thepresent invention is to provide an electrochromic mirror having a thirdsurface reflector/electrode that is at least partially transmissive atleast in regions in front of a light source, such as a display,illuminator, or signal light. An additional aspect of the presentinvention is to provide a third surface reflector/electrode (i.e.,second electrode) that is at least partially reflective in those regionsin front of the light source so as to provide an aesthetically pleasingappearance. Still another aspect of the present invention is to providea coating for the third surface of an electrochromic mirror thatfunctions as an electrode and as a reflector while allowing light havingwavelengths corresponding to a display to be transmitted through themirror. Still another aspect of the present invention is to provide anelectrochromic mirror having a partially reflective, partiallytransmissive electrode that does not have too yellow a hue and hasrelative color neutrality.

[0021] To achieve these and other aspects and advantages, theelectrochromic mirror according to the present invention comprises frontand rear elements having front and rear surfaces and being sealablybonded together in a spaced-apart relationship to define a chamber; atransparent first electrode including a layer of conductive materialcarried on a surface of one of the elements; an electrochromic materialcontained in the chamber; and a partially transmissive, partiallyreflective second electrode disposed over substantially all of the frontsurface of the rear element. The electrochromic rearview mirror soconstructed, has a reflectance of at least about 35% and a transmittanceof at least about 5% in at least portions of the visible spectrum. Themirror preferably further exhibits relative color neutrality with a C*value of less than about 20. Further, the mirror preferably does nothave a perceivable yellow hue and thus has a b* value less than about15.

[0022] Another aspect of the present invention is to provide a rearviewmirror assembly having a light emitting display assembly mounted behindthe mirror within the mirror housing whereby spurious reflections andghost images are substantially reduced or eliminated. To achieve thisand other aspects and advantages, a rearview mirror assembly accordingto the present invention comprises a housing adapted to be mounted tothe vehicle; front and rear elements mounted in the housing, theelements each having front and rear surfaces and being sealably bondedtogether in a spaced-apart relationship to define a chamber; anelectrochromic material contained in the chamber; a transparent firstelectrode including a layer of conductive material carried on a surfaceof one of the elements; a second electrode disposed on the front surfaceof the rear element; and a light emitting display mounted in thehousing. Either the second electrode is reflective or a separatereflector is provided on the rear surface of the rear element, thereflective electrode/reflector being at least partially transmissive inat least a location in front of the display. The display has a frontsurface and is preferably mounted behind the rear surface of the rearelement, such that the front surface of the display is not parallel withthe rear surface of the mirror. Alternatively, the display may have anon-specular front surface or the front surface could be laminateddirectly onto the back of the mirror. As yet another alternative, ananti-reflection coating may be applied to the reflective surface(s) ofthe display and the front surface of the mirror. Still anotheralternative to achieve the above aspects and advantages is to provide atleast one masking component that minimizes light that is emitted fromthe display from reflecting off of the reflector back toward the displayand then reflecting back off the front surface of the display toward thefront surface of the front element then on to the viewer.

[0023] An additional aspect of the present invention is to provide arearview mirror assembly including a light emitting display, whereby thedisplay is mounted in front of the reflective layer of the mirror. Toachieve these and other aspects of the present invention, a lightemitting display may be used that is substantially transparent andmounted either to the front surface of the front element or mounted inthe chamber defined between the front and rear elements. A preferredtransparent light emitting display is an organic light emitting diodedisplay.

[0024] Another aspect of the present invention is to provide an exteriorrearview mirror assembly incorporating a light source for illuminating aportion of the exterior of the vehicle, such as the door handle andlocking mechanism area of a vehicle door. To achieve these and otheraspects and advantages, an exterior rearview mirror assembly of thepresent invention comprises a housing adapted to be mounted to theexterior of the vehicle; a first element mounted in the housing, theelement having a front and rear surface; a reflector disposed on one ofthe surfaces of the first element; and a light source mounted in thehousing behind the rear surface of the first element, the light sourcebeing positioned within the housing so as to emit light, when activated,through the first element and through a region of the reflector that isat least partially transmissive toward a side of a vehicle. Such arearview mirror assembly thus conveniently illuminates areas on theoutside of the vehicle such as the door handles and locking mechanisms.

[0025] Another aspect of the invention is to locate a light sensor, suchas that used to sense ambient light in an electrochromic mirrorassembly, behind a reflective portion of the mirror while providing forincreased sensing area for light collection behind the electrochromicmedia and reflective portion of the mirror without the distractiveappearance resulting from missing patches of reflective material in themirror. To achieve these and other aspects and advantages, anelectrochromic mirror of the present invention comprises a housingadapted to be mounted to the vehicle; front and rear elements mounted insaid housing, the elements each having front and rear surfaces and beingsealably bonded together in a spaced-apart relationship to define achamber; a transparent first electrode including a layer of conductivematerial carried on a surface of one of the elements; a second electrodedisposed on the front surface of the rear element, wherein either saidsecond electrode is a reflective electrode or a separate reflector isdisposed over substantially all of the rear surface of the rear element,the reflective electrode/reflector being partially transmissive andpartially reflective over substantially all of one of the surfaces ofthe rear element; an electrochromic material contained in the chamber;and a light sensor mounted in the housing behind the rear element andbehind the partially transmissive, partially reflectiveelectrode/reflector.

[0026] In accordance with another embodiment of the present invention, arearview mirror assembly for a vehicle comprises: a housing adapted tobe mounted to the vehicle; front and rear elements mounted in thehousing, the elements each having front and rear surfaces and beingsealably bonded together in a spaced-apart relationship to define achamber; a transparent first electrode including a layer of conductivematerial carried on a surface of one of the elements; a second electrodedisposed on the front surface of the rear element; an electrochromicmaterial contained in the chamber; and a graphic display positioned inthe housing behind said rear element, wherein either the secondelectrode is a reflective electrode or a separate reflector is disposedover substantially all of the rear surface of the rear element, thereflective electrode/reflector being partially transmissive andpartially reflective in at least a location in front of the graphicdisplay.

[0027] These and other features, advantages, and objects of the presentinvention will be further understood and appreciated by those skilled inthe art by reference to the following specification, claims, andappended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In the drawings:

[0029]FIG. 1 is an enlarged cross-sectional view of a prior artelectrochromic mirror assembly;

[0030]FIG. 2 is a front elevational view schematically illustrating aninside/outside electrochromic rearview mirror system for motor vehicles,where the inside and outside mirrors incorporate the mirror assembly ofthe present invention;

[0031]FIG. 3 is an enlarged cross-sectional view of the insideelectrochromic rearview mirror incorporating a third surfacereflector/electrode illustrated in FIG. 2, taken on the line 3-3′thereof;

[0032]FIG. 4 is an enlarged cross-sectional view of an electrochromicmirror incorporating an alternate embodiment of a third surfacereflector/electrode according to the present invention;

[0033]FIG. 5a is an enlarged cross-sectional view of an electrochromicmirror having an improved arrangement for applying a drive potential tothe transparent conductor on the second surface of the mirror;

[0034]FIG. 5b is an enlarged top view of the third surface reflector ofFIG. 5a;

[0035]FIG. 6 is an enlarged cross-sectional view of an electrochromicmirror using a cured and machine-milled epoxy seal to hold thetransparent elements in a spaced-apart relationship;

[0036] FIGS. 7A-7G are partial cross-sectional views of alternativeconstructions of the electrochromic mirror according to the presentinvention as taken along line 7-7′ shown in FIG. 2;

[0037]FIG. 8 is a partial cross-sectional view of the electrochromicmirror according to the present invention as taken along line 7-7′ shownin FIG. 2;

[0038] FIGS. 9A-9E are partial cross-sectional views of additionalalternative constructions of the electrochromic mirror according to thepresent invention as taken along lines 7-7′ shown in FIG. 2;

[0039]FIG. 10 is a front elevational view schematically illustrating aninside electrochromic rearview mirror incorporating the mirror assemblyof the present invention;

[0040]FIG. 11 is a partial cross-sectional view of the electrochromicmirror shown in FIG. 10 taken along line 11-11′;

[0041]FIG. 12 is a perspective view of an outside automatic rearviewmirror including a signal light and an electrical circuit diagram inblock form of an outside rearview mirror assembly constructed inaccordance with the present invention;

[0042]FIG. 13 is a front elevational view of a signal light subassemblythat may be used in the outside mirror assembly of the presentinvention;

[0043]FIG. 14A is a partial cross-sectional view taken along line 14-14′of FIG. 12 illustrating one construction of the outside rearview mirrorof the present invention;

[0044]FIG. 14B is a partial cross-sectional view taken along line 14-14′of FIG. 12 illustrating a second alternative arrangement of the outsiderearview mirror constructed in accordance with the second embodiment ofthe present invention;

[0045]FIG. 14C is a partial cross-sectional view taken along lines14-14′ of FIG. 12 illustrating a third alternative arrangement of theoutside rearview mirror constructed in accordance with the secondembodiment of the present invention;

[0046]FIG. 14D is a partial cross-sectional view taken along lines14-14′ of FIG. 12 illustrating a fourth alternative arrangement of theoutside rearview mirror constructed in accordance with anotherembodiment of the present invention;

[0047]FIG. 15 is a pictorial representation of two vehicles, one ofwhich includes the signal mirror of the present invention;

[0048]FIG. 16 is a front elevational view of an automatic rearviewmirror embodying the information display area of another embodiment ofthe present invention;

[0049]FIG. 17 is an enlarged cross-sectional view, with portions brokenaway for clarity of illustration, of the automatic rearview mirrorillustrated in FIG. 16;

[0050]FIG. 18 is a front elevational view of the information displayarea, with portions broken away for clarity of illustration, of theautomatic rearview mirror illustrated in FIG. 16;

[0051]FIG. 19 is a perspective view of a signal light assembly for usewith another embodiment of the present invention;

[0052]FIG. 20 is a front elevational view of an outside rearview mirrorassembly constructed in accordance with another embodiment of thepresent invention;

[0053]FIG. 21 is a partial cross-sectional view of the rearview mirrorassembly shown in FIG. 20 taken along line 21-21′;

[0054]FIG. 22 is a perspective view of an exterior portion of anexemplary vehicle embodying the outside rearview mirror of the presentinvention as illustrated in FIGS. 20 and 21;

[0055]FIG. 23A is a front perspective view of a mask bearing indicia inaccordance with another aspect of the present invention;

[0056]FIG. 23B is a front perspective view of a rearview mirrorconstructed in accordance with another aspect of the present invention;

[0057]FIG. 24 is a front perspective view of a circuit board containinga plurality of light sources arranged in a configuration useful as adisplay in accordance with one aspect of the present invention; and

[0058]FIG. 25 is a cross-sectional view of a display and mirrorconstructed in accordance with one aspect of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0059]FIG. 2 shows a front elevational view schematically illustratingan inside mirror assembly 110 and two outside rearview mirror assemblies111 a and 111 b for the driver-side and passenger-side, respectively,all of which are adapted to be installed on a motor vehicle in aconventional manner and where the mirrors face the rear of the vehicleand can be viewed by the driver of the vehicle to provide a rearwardview. Inside mirror assembly 110 and outside rearview mirror assemblies111 a and 111 b may incorporate light-sensing electronic circuitry ofthe type illustrated and described in the above-referenced CanadianPatent No. 1,300,945, U.S. Pat. No. 5,204,778, or U.S. Pat. No.5,451,822, and other circuits capable of sensing glare and ambient lightand supplying a drive voltage to the electrochromic element.

[0060] Mirror assemblies 110, 111 a, and 111 b are essentially identicalin that like numbers identify components of the inside and outsidemirrors. These components may be slightly different in configuration,but function in substantially the same manner and obtain substantiallythe same results as similarly numbered components. For example, theshape of the front glass element of inside mirror 110 is generallylonger and narrower than outside mirrors 111 a and 111 b. There are alsosome different performance standards placed on inside mirror 110compared with outside mirrors 111 a and 111 b. For example, insidemirror 110 generally, when fully cleared, should have a reflectancevalue of about 70 percent to about 85 percent or higher, whereas theoutside mirrors often have a reflectance of about 50 percent to about 65percent. Also, in the United States (as supplied by the automobilemanufacturers), the passenger-side mirror 111 b typically has aspherically bent or convex shape, whereas the driver-side mirror 111 aand inside mirror 110 presently must be flat. In Europe, the driver-sidemirror 111 a is commonly flat or aspheric, whereas the passenger-sidemirror 111 b has a convex shape. In Japan, both outside mirrors have aconvex shape. The following description is generally applicable to allmirror assemblies of the present invention.

[0061]FIG. 3 shows a cross-sectional view of mirror assembly 110 havinga front transparent element 112 having a front surface 112 a and a rearsurface 112 b, and a rear element 114 having a front surface 114 a and arear surface 114 b. For clarity of description of such a structure, thefollowing designations will be used hereinafter. The front surface 112 aof the front glass element will be referred to as the first surface, andthe back surface 112 b of the front glass element as the second surface.The front surface 114 a of the rear glass element will be referred to asthe third surface, and the back surface 114 b of the rear glass elementas the fourth surface. A chamber 125 is defined by a layer oftransparent conductor 128 (carried on second surface 112 b), areflector/electrode 120 (disposed on third surface 114 a), and an innercircumferential wall 132 of sealing member 116. An electrochromic medium126 is contained within chamber 125.

[0062] As broadly used and described herein, the reference to anelectrode or layer as being “carried” on a surface of an element, refersto both electrodes or layers that are disposed directly on the surfaceof an element or disposed on another coating, layer or layers that aredisposed directly on the surface of the element.

[0063] Front transparent element 112 may be any material which istransparent and has sufficient strength to be able to operate in theconditions, e.g., varying temperatures and pressures, commonly found inthe automotive environment. Front element 112 may comprise any type ofborosilicate glass, soda lime glass, float glass, or any other material,such as, for example, a polymer or plastic, that is transparent in thevisible region of the electromagnetic spectrum. Front element 112 ispreferably a sheet of glass. The rear element must meet the operationalconditions outlined above, except that it does not need to betransparent in all applications, and therefore may comprise polymers,metals, glass, ceramics, and preferably is a sheet of glass.

[0064] The coatings of the third surface 114 a are sealably bonded tothe coatings on the second surface 112 b in a spaced-apart and parallelrelationship by a seal member 116 disposed near the outer perimeter ofboth second surface 112 b and third surface 114 a. Seal member 116 maybe any material that is capable of adhesively bonding the coatings onthe second surface 112 b to the coatings on the third surface 114 a toseal the perimeter such that electrochromic material 126 does not leakfrom chamber 125. Optionally, the layer of transparent conductivecoating 128 and the layer of reflector/electrode 120 may be removed overa portion where the seal member is disposed (not the entire portion,otherwise the drive potential could not be applied to the two coatings).In such a case, seal member 116 must bond well to glass.

[0065] The performance requirements for a perimeter seal member 116 usedin an electrochromic device are similar to those for a perimeter sealused in a liquid crystal device (LCD), which are well known in the art.The seal must have good adhesion to glass, metals and metal oxides; musthave low permeabilities for oxygen, moisture vapor, and otherdetrimental vapors and gases; and must not interact with or poison theelectrochromic or liquid crystal material it is meant to contain andprotect. The perimeter seal can be applied by means commonly used in theLCD industry, such as by silk-screening or dispensing. Totally hermeticseals, such as those made with glass frit or solder glass, can be used,but the high temperatures involved in processing (usually near 450° C.)this type of seal can cause numerous problems, such as glass substratewarpage, changes in the properties of transparent conductive electrode,and oxidation or degradation of the reflector. Because of their lowerprocessing temperatures, thermoplastic, thermosetting or UV curingorganic sealing resins are preferred. Such organic resin sealing systemsfor LCDs are described in U.S. Pat. Nos. 4,297,401, 4,418,102,4,695,490, 5,596,023, and 5,596,024. Because of their excellent adhesionto glass, low oxygen permeability and good solvent resistance,epoxy-based organic sealing resins are preferred. These epoxy resinseals may be UV curing, such as described in U.S. Pat. No. 4,297,401, orthermally curing, such as with mixtures of liquid epoxy resin withliquid polyamide resin or dicyandiamide, or they can be homopolymerized.The epoxy resin may contain fillers or thickeners to reduce flow andshrinkage such as fumed silica, silica, mica, clay, calcium carbonate,alumina, etc., and/or pigments to add color. Fillers pretreated withhydrophobic or silane surface treatments are preferred. Cured resincrosslink density can be controlled by use of mixtures ofmono-functional, di-functional, and multi-functional epoxy resins andcuring agents. Additives such as silanes or titanates can be used toimprove the seal's hydrolytic stability, and spacers such as glass beadsor rods can be used to control final seal thickness and substratespacing. Suitable epoxy resins for use in a perimeter seal member 116include, but are not limited to: “EPON RESIN” 813, 825, 826, 828, 830,834, 862, 1001F, 1002F, 2012, DPS-155, 164, 1031, 1074, 58005, 58006,58034, 58901, 871, 872, and DPL-862 available from Shell Chemical Co.,Houston, Tex.; “ARALITE” GY 6010, GY 6020, CY 9579, GT 7071, XU 248, EPN1139, EPN 1138, PY 307, ECN 1235, ECN 1273, ECN 1280, MT 0163, MY 720,MY 0500, MY 0510, and PT 810 available from Ciba Geigy, Hawthorne, N.Y.;and “D.E.R.” 331, 317, 361, 383, 661, 662, 667, 732, 736, “D.E.N.” 431,438, 439 and 444 available from Dow Chemical Co., Midland, Mich.Suitable epoxy curing agents include V-15, V-25, and V-40 polyamidesfrom Shell Chemical Co.; “AJICURE” PN-23, PN-34, and VDH available fromAjinomoto Co., Tokyo, Japan; “CUREZOL” AMZ, 2MZ, 2E4MZ, C11Z, C17Z, 2PZ,21Z, and 2P4MZ available from Shikoku Fine Chemicals, Tokyo, Japan;“ERISYS” DDA or DDA accelerated with U-405, 24EMI, U-410, and U-415available from CVC Specialty Chemicals, Maple Shade, N.J.; and “AMICURE”PACM, 352, CG, CG-325, and CG-1200 available from Air Products,Allentown, Pa. Suitable fillers include fumed silica such as “CAB-O-SIL”L-90, LM-130, LM-5, PTG, M-5, MS-7, MS-55, TS-720, HS-5, and EH-5available from Cabot Corporation, Tuscola, Ill.; “AEROSIL” R972, R974,R805, R812, R812 S, R202, US204, and US206 available from Degussa,Akron, Ohio. Suitable clay fillers include BUCA, CATALPO, ASP NC,SATINTONE 5, SATINTONE SP-33, TRANSLINK 37, TRANSLINK 77, TRANSLINK 445,and TRANSLINK 555 available from Engelhard Corporation, Edison, N.J.Suitable silica fillers are SILCRON G-130, G-300, G-100-T, and G-100available from SCM Chemicals, Baltimore, Md. Suitable silane couplingagents to improve the seal's hydrolytic stability are Z-6020, Z-6030,Z-6032, Z-6040, Z-6075, and Z-6076 available from Dow CorningCorporation, Midland, Mich. Suitable precision glass microbead spacersare available in an assortment of sizes from Duke Scientific, Palo Alto,Calif.

[0066] The layer of a transparent electrically conductive material 128is deposited on the second surface 112 b to act as an electrode.Transparent conductive material 128 may be any material which bonds wellto front element 112, is resistant to corrosion to any materials withinthe electrochromic device, resistant to corrosion by the atmosphere, hasminimal diffuse or specular reflectance, high light transmission, nearneutral coloration, and good electrical conductance. Transparentconductive material 128 may be fluorine-doped tin oxide, doped zincoxide, zinc-doped indium oxide, indium tin oxide (ITO), ITO/metal/ITO(IMI) as disclosed in “Transparent Conductive Multilayer-Systems for FPDApplications,” by J. Stollenwerk, B. Ocker, K. H. Kretschmer of LEYBOLDAG, Alzenau, Germany, the materials described in above-referenced U.S.Pat. No. 5,202,787, such as TEC 20 or TEC 15, available from LibbeyOwens-Ford Co. of Toledo, Ohio, or other transparent conductors.Generally, the conductance of transparent conductive material 128 willdepend on its thickness and composition. IMI generally has superiorconductivity compared with the other materials. IMI is, however, knownto undergo more rapid environmental degradation and suffer frominterlayer delamination. The thickness of the various layers in the IMIstructure may vary, but generally the thickness of the first ITO layerranges from about 10 Å to about 200 Å, the metal ranges from about 10 Åto about 200 Å, and the second layer of ITO ranges from about 10 Å toabout 200 Å. If desired, an optional layer or layers of a colorsuppression material 130 may be deposited between transparent conductivematerial 128 and the second surface 112 b to suppress the reflection ofany unwanted portions of the electromagnetic spectrum.

[0067] In accordance with the present invention, a combinationreflector/electrode 120 is disposed on third surface 114 a.Reflector/electrode 120 comprises at least one layer of a reflectivematerial 121 which serves as a mirror reflectance layer and also formsan integral electrode in contact with and in a chemically andelectrochemically stable relationship with any constituents in anelectrochromic medium. As stated above, the conventional method ofbuilding electrochromic devices was to incorporate a transparentconductive material on the third surface as an electrode, and place areflector on the fourth surface. By combining the “reflector” and“electrode,” and placing both on the third surface, several unexpectedadvantages arise which not only make the device manufacture lesscomplex, but also allow the device to operate with higher performance.The following will outline the exemplary advantages of the combinedreflector/electrode of the present invention.

[0068] First, the combined reflector/electrode 120 on the third surfacegenerally has higher conductance than a conventional transparentelectrode and previously used reflector/electrodes, which will allowgreater design flexibility. One can either change the composition of thetransparent conductive electrode on the second surface to one that haslower conductance (being cheaper and easier to produce and manufacture)while maintaining coloration speeds similar to that obtainable with afourth surface reflector device, while at the same time decreasingsubstantially the overall cost and time to produce the electrochromicdevice. If, however, performance of a particular design is of utmostimportance, a moderate to high conductance transparent electrode can beused on the second surface, such as, for example, ITO, IMI, etc. Thecombination of a high conductance (i.e., less than 250 Ω/□, preferablyless than 15 Ω/□) reflector/electrode on the third surface and a highconductance transparent electrode on the second surface will not onlyproduce an electrochromic device with more even overall coloration, butwill also allow for increased speed of coloration and clearing.Furthermore, in fourth surface reflector mirror assemblies there are twotransparent electrodes with relatively low conductance, and inpreviously used third surface reflector mirrors there is a transparentelectrode and a reflector/electrode with relatively low conductance and,as such, a long buss bar on the front and rear element to bring currentin and out is necessary to ensure adequate coloring speed. The thirdsurface reflector/electrode of the present invention has a higherconductance and therefore has a very even voltage or potentialdistribution across the conductive surface, even with a small orirregular contact area. Thus, the present invention provides greaterdesign flexibility by allowing the electrical contact for the thirdsurface electrode to be very small while still maintaining adequatecoloring speed.

[0069] Second, a third surface reflector/electrode helps improve theimage being viewed through the mirror. FIG. 1 shows how light travelsthrough a conventional fourth surface reflector device. In the fourthsurface reflector, the light travels through: the first glass element,the transparent conductive electrode on the second surface, theelectrochromic media, the transparent conductive electrode on the thirdsurface, and the second glass element, before being reflected by thefourth surface reflector. Both transparent conductive electrodes exhibithighly specular transmittance but also possess diffuse transmittance andreflective components, whereas the reflective layer utilized in anyelectrochromic mirror is chosen primarily for its specular reflectance.By diffuse reflectance or transmittance component, we mean a materialwhich reflects or transmits a portion of any light impinging on itaccording to Lambert's law whereby the light rays are spread-about orscattered. By specular reflectance or transmittance component, we mean amaterial which reflects or transmits light impinging on it according toSnell's laws of reflection or refraction. In practical terms, diffusereflectors and transmitters tend to slightly blur images, whereasspecular reflectors show a crisp, clear image. Therefore, lighttraveling through a mirror having a device with a fourth surfacereflector has two partial diffuse reflectors (on the second and thirdsurface) which tend to blur the image, and a device with a third surfacereflector/electrode of the present invention only has one diffusereflector (on the second surface).

[0070] Additionally, because the transparent electrodes act as partialdiffuse transmitters, and the farther away the diffuse transmitter isfrom the reflecting surface the more severe the blurring becomes, amirror with a fourth surface reflector appears significantly more hazythan a mirror with a third surface reflector. For example, in the fourthsurface reflector shown in FIG. 1, the diffuse transmitter on the secondsurface is separated from the reflector by the electrochromic material,the second conductive electrode, and the second glass element. Thediffuse transmitter on the third surface is separated from the reflectorby the second glass element. By incorporating a combinedreflector/electrode on the third surface in accordance with the presentinvention, one of the diffuse transmitters is removed, and the distancebetween the reflector and the remaining diffuse transmitter is closer bythe thickness of the rear glass element. Therefore, the third surfacemetal reflector/electrode of the present invention provides anelectrochromic mirror with a superior viewing image.

[0071] Finally, a third surface metal reflector/electrode improves theability to reduce double imaging in an electrochromic mirror. As statedabove, there are several interfaces where reflections can occur. Some ofthese reflections can be significantly reduced with color suppression oranti-reflective coatings; however, the most significant “double imaging”reflections are caused by misalignment of the first surface and thesurface containing the reflector, and the most reproducible way ofminimizing the impact of this reflection is by ensuring both glasselements are parallel. Presently, convex glass is often used for thepassenger side outside mirror and aspheric glass is sometimes used forthe driver side outside mirror to increase the field of view and reducepotential blind spots. However, it is difficult to reproducibly bendsuccessive elements of glass having identical radii of curvature.Therefore, when building an electrochromic mirror, the front glasselement and the rear glass element may not be perfectly parallel (do nothave identical radii of curvature), and therefore, the otherwisecontrolled double imaging problems become much more pronounced. Byincorporating a combined reflector electrode on the third surface of thedevice in accordance with the present invention, light does not have totravel through the rear glass element before being reflected, and anydouble imaging that occurs from the elements being out of parallel willbe significantly reduced.

[0072] It is desirable in the construction of outside rearview mirrorsto incorporate thinner glass in order to decrease the overall weight ofthe mirror so that the mechanisms used to manipulate the orientation ofthe mirror are not overloaded. Decreasing the weight of the device alsoimproves the dynamic stability of the mirror assembly when exposed tovibrations. Heretofore, no electrochromic mirrors incorporating asolution-phase electrochromic medium and two thin glass elements havebeen commercially available, because thin glass suffers from beingflexible and prone to warpage or breakage, especially when exposed toextreme environments. This problem is substantially improved by using animproved electrochromic device incorporating two thin glass elementshaving an improved gel material. This improved device is disclosed incommonly assigned U.S. Pat. No. 5,940,201 entitled “AN ELECTROCHROMICMIRROR WITH TWO THIN GLASS ELEMENTS AND A GELLED ELECTROCHROMIC MEDIUM,”filed on or about Apr. 2, 1997. The entire disclosure, including thereferences contained therein, of this patent is incorporated herein byreference. The addition of the combined reflector/electrode onto thethird surface of the device further helps remove any residual doubleimaging resulting from the two glass elements being out of parallel.

[0073] The most important factors for obtaining a reliableelectrochromic mirror having a third surface reflector/electrode 120 arethat the reflector/electrode have sufficient reflectance and that themirror incorporating the reflector/electrode has adequate operationallife. Regarding reflectance, the automobile manufacturers prefer areflective mirror for the inside mirror having a reflectivity of atleast 60 percent, whereas the reflectivity requirements for an outsidemirror are less stringent and generally must be at least 35 percent.

[0074] To produce an electrochromic mirror with 70 percent reflectance,the reflector must have a reflectance higher than 70 percent because theelectrochromic medium in front of the reflector reduces the reflectancefrom the reflector interface as compared to having the reflector in airdue to the medium having a higher index of refraction as compared toair. Also, the glass, the transparent electrode, and the electrochromicmedium even in its clear state are slightly light absorbing. Typically,if an overall reflectance of 65 percent is desired, the reflector musthave a reflectance of about 75 percent.

[0075] Regarding operational life, the layer or layers that comprise thereflector/electrode 120 must have adequate bond strength to theperipheral seal, the outermost layer must have good shelf life betweenthe time it is coated and the time the mirror is assembled, the layer orlayers must be resistant to atmospheric and electrical contactcorrosion, and must bond well to the glass surface or to other layersdisposed beneath it, e.g., the base or intermediate layer (122 or 123,respectively). The overall sheet resistance for the reflector/electrode120 may range from about 0.01 Ω/□ to about 100 Ω/□ and preferably rangesfrom about 0.2 Ω/□ to about 25 Ω/□. As will be discussed in more detailbelow, improved electrical interconnections using a portion of the thirdsurface reflector/electrode as a high conductance contact or buss barfor the second surface transparent conductive electrode may be utilizedwhen the conductance of the third surface reflector/electrode is belowabout 2 Ω/□.

[0076] Referring to FIG. 3 for one embodiment of the present invention,a reflector/electrode that is made from a single layer of a reflectivesilver or silver alloy 121 is provided that is in contact with at leastone solution-phase electrochromic material. The layer of silver orsilver alloy covers the entire third surface 114 a of second element114. The reflective silver alloy means a homogeneous or non-homogeneousmixture of silver and one or more metals, or an unsaturated, saturated,or supersaturated solid solution of silver and one or more metals. Thethickness of reflective layer 121 ranges from about 50 Å to about 2000Å, and more preferably from about 200 Å to about 1000 Å. If reflectivelayer 121 is disposed directly to the glass surface, it is preferredthat the glass surface be treated by plasma discharge to improveadhesion.

[0077] Table 1 shows the relevant properties for a number of differentmetals that have been proposed for third surface reflectors as comparedwith the materials suitable for the reflector/electrode 120 of thepresent invention. The only materials in Table 1 having reflectanceproperties suitable for use as a third surface reflector/electrode incontact with at least one solution-phase electrochromic material for aninside electrochromic mirror for a motor vehicle are aluminum, silver,and silver alloys. Aluminum performs very poorly when in contact withsolution-phase material(s) in the electrochromic medium because aluminumreacts with or is corroded by these materials. The reacted or corrodedaluminum is non-reflective and non-conductive and will typicallydissolve off, flake off, or delaminate from the glass surface. Silver ismore stable than aluminum but can fail when deposited over the entirethird surface because it does not have long shelf life and is notresistant to electrical contact corrosion when exposed to theenvironmental extremes found in the motor vehicle environment. Theseenvironmental extremes include temperatures ranging from about −40° C.to about 85° C., and humidities ranging from about 0 percent to about100 percent. Further, mirrors must survive at these temperatures andhumidities for coloration cycle lives up to 100,000 cycles. The otherprior art materials (silver/copper, chromium, stainless steel, rhodium,platinum, palladium, Inconel®, copper, or titanium) suffer from any oneof a number of deficiencies such as: very poor color neutrality(silver/copper and copper); poor reflectance (chromium, stainless steel,rhodium, molybdenum, platinum, palladium, Inconel®, and titanium); poorcleanability (chromium); or poor electrical contact stability (chromium,stainless steel and molybdenum).

[0078] When silver is alloyed with certain materials to produce a thirdsurface reflector/electrode, the deficiencies associated with silvermetal and aluminum metal can be overcome. Suitable materials for thereflective layer are alloys of silver/palladium, silver/gold,silver/platinum, silver/rhodium, silver/titanium, etc. The amount of thesolute material, i.e., palladium, gold, etc., can vary. As can be seenfrom Table 1, the silver alloys surprisingly retain the high reflectanceand low sheet resistance properties of silver, while simultaneouslyimproving their contact stability, shelf life, and also increasing theirwindow of potential stability when used as electrodes in propylenecarbonate containing 0.2 molar tetraethylammonium tetrafluoroborate. Thepresently preferred materials for reflective layer 121 are silver/gold,silver/platinum, and silver/palladium.

[0079] More typically, reflector/electrode 120 has, in addition to thelayer of a reflective alloy 121, an optional base layer of a conductivemetal or alloy 122 deposited directly on the third surface 114 a. Theremay also be an optional intermediate layer of a conductive metal oralloy 123 disposed between the layer of reflective material 121 and thebase coat 122. If reflector/electrode 120 includes more than one layer,there should not be galvanic corrosion between the two metals or alloys.If optional base layer 122 is deposited between the reflective layer 121and the glass element 114, it should be environmentally rugged, e.g.,bond well to the third (glass) surface 114 a and to reflective layer121, and maintain this bond when the seal 116 is bonded to thereflective layer. Base layer 122 may have a thickness from about 50 Å toabout 2000 Å, and more preferably from about 100 Å to about 1000 Å.Suitable materials for the base layer 122 are chromium, stainless steel,titanium, and alloys of chromium/molybdenum/nickel, molybdenum, andnickel-based alloys (commonly referred to as Inconel®, available fromCastle Metals, Chicago, Ill.). The main constituents of Inconel® arenickel which may range from 52 percent to 76 percent (Inconel® 617 and600, respectfully), iron which may range from 1.5 percent to 18.5percent (Inconel® 617 and Inconel® 718, respectfully), and chromiumwhich may range from 15 percent to 23 percent (Inconel® 600 and Inconel®601, respectfully). Inconel® 617 having 52 percent nickel, 1.5 percentiron, 22 percent chromium, and typical “other” constituents including12.5 percent cobalt, 9.0 percent molybdenum, and 1.2 percent aluminumwas used in the present examples.

[0080] In some instances it is desirable to provide an optionalintermediate layer 123 between the reflective layer 121 and the baselayer 122 in case the material of layer 121 does not adhere well to thematerial of layer 122 or there are any adverse interactions between thematerials, e.g., galvanic corrosion. If used, intermediate layer 123should exhibit environmental ruggedness, e.g., bond well to the baselayer 122 and to the reflective layer 121, and maintain this bond whenthe seal member 116 is bonded to the reflective layer 121. The thicknessof intermediate layer 123 ranges from about 10 Å to about 2000 Å, andmore preferably from about 100 Å to about 1000 Å. Suitable materials forthe optional intermediate layer 123 are molybdenum, rhodium, stainlesssteel, titanium, copper, nickel, gold, platinum, and alloys thereof.Reference is made to examples 1 and 2 to show how the insertion of arhodium intermediate layer between a chromium base layer and a silver orsilver alloy reflective layer increases the time to failure incopper-accelerated acetic acid-salt spray (CASS) by a factor of 10.Example 4 shows how the insertion of a molybdenum intermediate layerbetween a chromium base layer and a silver alloy having a molybdenumflash over-coat layer increases the time to failure in CASS by a factorof 12.

[0081] Finally, it is sometimes desirable to provide an optional flashover-coat 124 over reflective layer 121, such that it (and not thereflective layer 121) contacts the electrochromic medium. This flashover-coat layer 124 must have stable behavior as an electrode, it musthave good shelf life, it must bond well to the reflective layer 121, andmaintain this bond when the seal member 116 is bonded thereto. It mustbe sufficiently thin, such that it does not completely block thereflectivity of reflective layer 121. In accordance with anotherembodiment of the present invention, when a very thin flash over-coat124 is placed over the highly reflecting layer, then the reflectivelayer 121 may be silver metal or a silver alloy because the flash layerprotects the reflective layer while still allowing the highly reflectinglayer 121 to contribute to the reflectivity of the mirror. In suchcases, a thin (between about 25 Å and about 300 Å) layer of rhodium,platinum, or molybdenum is deposited over the reflective layer 121. Whenreflective layer 121 is silver, flash layer 122 may also be a silveralloy.

[0082] It is preferred but not essential that the third surfacereflector/electrode 120 be maintained as the cathode in the circuitrybecause this eliminates the possibility of anodic dissolution or anodiccorrosion that might occur if the reflector/electrode was used as theanode. Although as can be seen in Table 1, if certain silver alloys areused, the positive potential limit of stability extends out far enough,e.g., 1.2 V, that the silver alloy reflector/electrode could safely beused as the anode in contact with at least one solution-phaseelectrochromic material. TABLE 1 Negative Potential Positive LimitPotential of Limit Window Window Reflect- of of White Light ancePotential Potential Reflectance In Device Contact Stability StabilityMetal In Air (%) Stability (V) (V) Al >92 N/A very N/A N/A poor Cr 65N/A poor N/A N/A Stain- 60 N/A good N/A N/A less Steel Rh 75 N/A veryN/A N/A good Pt 72 N/A very N/A N/A good Inconel 55 N/A N/A N/A N/A Ag97 84 fair −2.29 0.86 Ag2.7Pd 93 81 good −2.26 0.87 Ag10Pd 80 68 good−2.05 0.97 Ag6Pt 92 80 good −1.66* 0.91 Ag6Au 96 84 good −2.25 0.98Ag25Au 94 82 good −2.3 1.2

[0083] The various layers of reflector/electrode 120 can be deposited bya variety of deposition procedures, such as RF and DC sputtering, e-beamevaporation, chemical vapor deposition, electrode position, etc., thatwill be known to those skilled in the art. The preferred alloys arepreferably deposited by sputtering (RF or DC) a target of the desiredalloy or by sputtering separate targets of the individual metals thatmake up the desired alloy, such that the metals mix during thedeposition process and the desired alloy is produced when the mixedmetals deposit and solidify on the substrate surface.

[0084] In another embodiment, the reflector/electrode 120 shown in FIG.4 has at least two layers (121 and 122), where at least one layer of abase material 122 covers substantially the entire portion of the thirdsurface 114 a and at least one layer of a reflective material 121 coversthe inner section of the third surface 114 a, but does not cover theperipheral edge portion 125 where seal member 116 is disposed.Peripheral portion 125 may be created by masking that portion of layer122 during deposition of the layer of reflective material 121, or thelayer of reflective material may be deposited over the entire thirdsurface and subsequently removed or partially removed in the peripheralportion. The masking of layer 122 may be accomplished by use of aphysical mask or through other well-known techniques, such asphotolithography and the like. Alternatively, layer 122 may be partiallyremoved in the peripheral portion by a variety of techniques, such as,for example, by etching (laser, chemical, or otherwise), mechanicalscraping, sandblasting, or otherwise. Laser etching is the presentlypreferred method because of its accuracy, speed, and control. Partialremoval is preferably accomplished by laser etching in a pattern whereenough metal is removed to allow the seal member 116 to bond directly tothe third surface 114 a while leaving enough metal in this area suchthat the conductance in this area is not significantly reduced.

[0085] In addition, an optional intermediate layer of a conductivematerial 123 may be placed over the entire area of third surface 114 aand disposed between the reflective layer 121 and the base layer 122, orit may be placed only under the area covered by layer 121, i.e., not inperipheral edge portion 125. If this optional intermediate layer isutilized, it can cover the entire area of third surface 114 a or it maybe masked or removed from the peripheral edge portion as discussedabove.

[0086] An optional flash over-coat layer 124 may be coated over thereflective layer 121. The reflective layer 121, the optionalintermediate layer 123, and the base layer 122 preferably haveproperties similar to that described above, except that the layer ofreflective material 121 need not bond well to the epoxy seal, since itis removed in the peripheral portion where the seal member 116 isplaced. Because the interaction with the epoxy seal is removed, silvermetal itself, in addition to the alloys of silver described above, willfunction as the reflective layer. Alternatively, an adhesion promotercan be added to the sealing material which enhances adhesion to silveror silver alloys and the reflective layer can be deposited over most ofthe third surface including substantial portions under the seal area.Such adhesion promoters are disclosed in U.S. Pat. No. 6,157,480,entitled “IMPROVED SEAL FOR ELECTROCHROMIC DEVICES,” the disclosure ofwhich is incorporated herein by reference.

[0087] Referring again to FIG. 3, chamber 125, defined by transparentconductor 128 (disposed on front element rear surface 112 b),reflector/electrode 120 (disposed on rear element front surface 114 a),and an inner circumferential wall 132 of sealing member 116, contains anelectrochromic medium 126. Electrochromic medium 126 is capable ofattenuating light traveling therethrough and has at least onesolution-phase electrochromic material in intimate contact withreflector/electrode 120 and at least one additional electroactivematerial that may be solution-phase, surface-confined, or one thatplates out onto a surface. However, the presently preferred media aresolution-phase redox electrochromics, such as those disclosed inabove-referenced U.S. Pat. Nos. 4,902,108, 5,128,799, 5,278,693,5,280,380, 5,282,077, 5,294,376, and 5,336,448. U.S. Pat. No. 6,020,987,entitled “AN IMPROVED ELECTROCHROMIC MEDIUM CAPABLE OF PRODUCING APRE-SELECTED COLOR,” discloses electrochromic media that are perceivedto be gray throughout their normal range of operation. The entiredisclosure of this patent is hereby incorporated herein by reference. Ifa solution-phase electrochromic medium is utilized, it may be insertedinto chamber 125 through a sealable fill port 142 through well-knowntechniques, such as vacuum backfilling and the like.

[0088] A resistive heater 138, disposed on the fourth glass surface 114b, may optionally be a layer of ITO, fluorine-doped tin oxide, or may beother heater layers or structures well known in the art. Electricallyconductive spring clips 134 a and 134 b are placed on the coated glasssheets (112 and 114) to make electrical contact with the exposed areasof the transparent conductive coating 128 (clip 134 b) and the thirdsurface reflector/electrode 120 (clip 134 a). Suitable electricalconductors (not shown) may be soldered or otherwise connected to thespring clips (134 a and 134 b) so that a desired voltage may be appliedto the device from a suitable power source.

[0089] An electrical circuit 150, such as those taught in theabove-referenced Canadian Patent No. 1,300945 and U.S. Pat. Nos.5,204,778, 5,434,407, and 5,451,822, is connected to and allows controlof the potential to be applied across reflector/electrode 120 andtransparent electrode 128, such that electrochromic medium 126 willdarken and thereby attenuate various amounts of light travelingtherethrough and thus vary the reflectance of the mirror containingelectrochromic medium 126.

[0090] As stated above, the low resistance of reflector/electrode 120allows greater design flexibility by allowing the electrical contact forthe third surface reflector/electrode to be small while maintainingadequate coloring speed. This flexibility extends to improving theinterconnection techniques to the layer of transparent conductivematerial 128 on the second surface 112 b. Referring now to FIGS. 5a and5 b, an improved mechanism for applying a drive potential to the layerof transparent conductive material 128 is shown. Electrical connectionbetween the power supply and the layer of transparent conductivematerial 128 is made by connecting the buss bars (or clips 119 a) to thearea of reflector/electrode 120 a, such that the drive potential travelsthrough the area of reflector/electrode 120 a and conductive particles116 b in sealing member 116 before reaching the transparent conductor128. The reflector/electrode must not be present in area 120 c, so thatthere is no chance of current flow from reflector/electrode area 120 ato 120 b. This configuration is advantageous in that it allowsconnection to the transparent conductive material 128 nearly all the wayaround the circumference, and therefore improves the speed of dimmingand clearing of the electrochromic media 126.

[0091] In such a configuration, sealing member 116 comprises a typicalsealing material, e.g., epoxy 116 a, with conductive particles 116 bcontained therein. The conductive particles may be small, such as, forexample, gold, silver, copper, etc., coated plastic with a diameterranging from about 5 microns to about 80 microns, in which case theremust be a sufficient number of particles to ensure sufficientconductivity between the reflector/electrode area 120 a and thetransparent conductive material 128. Alternatively, the conductiveparticles may be large enough to act as spacers, such as, for example,gold, silver, copper, etc., coated glass or plastic beads. Thereflector/electrode 120 is separated into two distinctreflector/electrode areas (120 a and 120 b, separated by an area 120 cdevoid of reflector/electrode). There are many methods of removing thereflector/electrode 120 from area 120 c, such as, for example, chemicaletching, laser ablating, physical removal by scraping, etc. Depositionin area 120 c can also be avoided by use of a mask during deposition ofreflector/electrode. Sealing member 116 with particles 116 b contactsarea 120 a such that there is a conductive path betweenreflector/electrode area 120 a and the layer of transparent conductivematerial 128. Thus, electrical connection to the reflector/electrodearea 120 b that imparts a potential to the electrochromic medium isconnected through clips 119 b to the electronic circuitry atreflector/electrode area 120 d (FIG. 5b). No conductive particles 116 bcan be placed in this reflector/electrode area 120 b because of thepossibility of an electrical short between reflector/electrode area 120b and the layer of transparent conductive material 128. If such anelectrical short occurred, the electrochromic device would not operateproperly. Additionally, no conductive seal 116 b should be present inarea 120 b.

[0092] A variety of methods can be used to ensure that no conductiveparticles 116 b enter into this reflector/electrode area 120 b, such as,for example, disposing a nonconductive material into the area 120 c ofreflector/electrode devoid of conductive material. A dual dispensercould be used to deposit the seal 116 with conductive particles 116 bonto reflector/electrode area 120 a and simultaneously deposit thenonconductive material into reflector/electrode area 120 c. Anothermethod would be to cure a nonconductive seal in area 120 c and thendispose a conductive material 116 c into the edge gap to electricallyinterconnect reflector/electrode area 120 a with transparent conductivelayer 128. A general method of ensuring that no conductive particlesreach reflector/electrode area 120 b is to make sure seal 116 has properflow characteristics, such that the conductive portion 116 b tends tostay behind as the sealant is squeezed out during assembly, and only thenon-conductive portion of 116 flows into area 120 b. In an alternativeembodiment, spacer member 116 need not contain conductive particles anda conductive member or material 116 c may be placed on or in the outeredge of member 116 to interconnect transparent conductive material 128to reflector/electrode area 120 a.

[0093] Yet another embodiment of an improved electrical interconnectiontechnique is illustrated in FIG. 6, where a first portion of seal member116 is applied directly onto the third surface 114 a and cured prior tothe application of reflector/electrode 120. After thereflector/electrode 120 is deposited onto the third surface 114 a overthe first portion of seal member 116, a portion of the cured seal member116 is machined off to leave 116 i as shown with a predeterminedthickness (which will vary depending on the desired cell spacing betweenthe second surface 112 b and the third surface 114 a). The cell spacingranges from about 20 microns to about 1500 microns, and preferablyranges from about 90 microns to about 750 microns. By curing the firstportion of seal member and machining it to a predetermined thickness(116 i), the need for glass beads to ensure a constant cell spacing iseliminated. Glass beads are useful to provide cell spacing, however,they provide stress points where they contact reflector/electrode 120and transparent conductor 128. By removing the glass beads, these stresspoints are also removed. During the machining, the reflector/electrode120 that is coated on first portion of seal member 116 is removed toleave an area devoid of reflector/electrode 120. A second portion ofseal member 116 ii is then deposited onto the machined area of the firstportion of seal member 116 i or on the coatings on second surface 112 bin the area corresponding to 116 i, and seal member 116 ii is curedafter assembly in a conventional manner. Finally, an outer conductiveseal member 117 may optionally be deposited on the outer peripheralportion of seal member 116 to make electrical contact between the outeredge of reflector/electrode 120 and the outer peripheral edge of thelayer of transparent conductive material 128. This configuration isadvantageous in that it allows connection to the transparent conductivematerial 128 nearly all the way around the circumference, and thereforeimproves the speed of dimming and clearing of the electrochromic media126.

[0094] Referring again to FIG. 2, rearview mirrors embodying the presentinvention preferably include a bezel 144, which extends around theentire periphery of each individual assembly 110, 111 a, and/or 111 b.The bezel 144 conceals and protects the spring clips 134 a and 134 b ofFIG. 3 (or 116 a and 116 b of FIG. 5a; 116 i, 116 ii, and 117 of FIG.6), and the peripheral edge portions of the sealing member and both thefront and rear glass elements (112 and 114, respectively). A widevariety of bezel designs are well known in the art, such as, forexample, the bezel taught and claimed in above-referenced U.S. Pat. No.5,448,397. There are also a wide variety of housings well known in theart for attaching the mirror assembly 110 to the inside front windshieldof an automobile, or for attaching the mirror assemblies 111 a and 111 bto the outside of an automobile. A preferred mounting bracket isdisclosed in above-referenced U.S. Pat. No. 5,337,948.

[0095] The electrical circuit preferably incorporates an ambient lightsensor (not shown) and a glare light sensor 160, the glare light sensorbeing positioned either behind the mirror glass and looking through asection of the mirror with the reflective material completely orpartially removed, or the glare light sensor can be positioned outsidethe reflective surfaces, e.g., in the bezel 144 or as described below,the sensor can be positioned behind a uniformly deposited transflectivecoating. Additionally, an area or areas of the electrode and reflector,such as 146, may be completely removed or partially removed as describedbelow to permit a vacuum fluorescent display, such as a compass, clock,or other indicia, to show through to the driver of the vehicle or asalso described below, this light emitting display assembly can be shownthrough a uniformly deposited transflective coating. The presentinvention is also applicable to a mirror which uses only one video chiplight sensor to measure both glare and ambient light and which isfurther capable of determining the direction of glare. An automaticmirror on the inside of a vehicle, constructed according to thisinvention, can also control one or both outside mirrors as slaves in anautomatic mirror system.

[0096] The following illustrative examples are not intended to limit thescope of the present invention but to illustrate its application anduse:

EXAMPLE 1

[0097] Electrochromic mirror devices incorporating a high reflectivitythird surface reflector/electrode were prepared by sequentiallydepositing approximately 700 Å of chromium and approximately 500 Å ofsilver on the surface of 2.3-mm thick sheets of flat soda lime floatglass cut to an automotive mirror element shape. A second set of highreflectivity third surface reflector/electrodes were also prepared bysequentially depositing 700 Å of chromium and approximately 500 Å of asilver alloy containing 3 percent by weight palladium on the glasselement shapes. The deposition was accomplished by passing the saidglass element shapes past separate metal targets in a magnetronsputtering system with a base pressure of 3×10⁻⁶ torr and an argonpressure of 3×10⁻³ torr.

[0098] The chromium/silver and chromium/silver 3 percent palladium alloycoated glass automotive mirror shapes were used as the rear planarelements of an electrochromic mirror device. The front element was asheet of TEC 15 transparent conductor coated glass from LOF cut similarin shape and size to the rear glass element. The front and rear elementswere bonded together by an epoxy perimeter seal, with the conductiveplanar surfaces facing each other and parallel to each other with anoffset. The spacing between the electrodes was about 137 microns. Thedevices were vacuum filled through a fill port left in the perimeterseal with an electrochromic solution made up of:

[0099] 0.028 molar 5,10-dihydro-5-10-dimethylphenazine

[0100] 0.034 molar 1,1′-di(3-phenyl(n-propane))-4,4′-bipyridiniumdi(tetrafluoroborate) 0.030 molar2-(2′-hydroxy-5′-methylphenyl)-benzotriazole

[0101] in a solution of 3 weight percent Elvacite™ 2051polymethylmethacrylate resin dissolved in propylene carbonate.

[0102] The fill port was plugged with an UV cure adhesive, which wascured by exposure to UV light.

[0103] The devices were subjected to accelerated durability tests untilthe seal integrity of the device was breached or the lamination of thereflector/electrode layers or the transparent electrode layers weresubstantially degraded or dilapidated, at which time the device is saidto fail. The first test performed was steam autoclave testing in whichthe devices were sealed in a water-containing vessel and subjected to120° C. at a pressure of 15 pounds per square inch (psi). The secondtest performed was copper-accelerated acetic acid-salt spray (CASS) asdescribed in ASTM B 368-85.

[0104] When the electrochromic devices were observed after one day intesting, all of the devices failed to withstand the CASS testing, andall of the devices failed to withstand the steam autoclave testing.

EXAMPLE 2

[0105] Other than as specifically mentioned, the devices in this examplewere constructed in accordance with the conditions and teachings inExample 1. Multilayer combination reflector/electrodes were prepared bysequentially depositing approximately 700 Å chromium, approximately 100Å rhodium, and approximately 500 Å of silver on the surface of the glasselement shapes. A second set of multilayer combinationreflector/electrodes were also prepared by sequentially depositingapproximately 700 Å of chromium, approximately 100 Å rhodium, andapproximately 500 Å of a silver alloy containing 3 percent by weightpalladium on the surface of said glass element shapes. Theelectrochromic devices were constructed and tested in accordance withExample 1.

[0106] The device incorporating the sequential multilayer combinationreflector electrode of chromium, rhodium, and silver withstood steamautoclave testing two times longer and CASS testing 10 times longer thanthe device in Example 1 before failure occurred. The deviceincorporating the sequential multilayer combination reflector electrodeof chromium, rhodium, and silver 3 percent palladium alloy withstoodsteam autoclave testing three times longer and CASS testing 10 timeslonger than devices in Example 1 before failure occurred.

EXAMPLE 3

[0107] Other than as specifically mentioned, the devices in this examplewere constructed in accordance with the conditions and teachings inExample 1. Multilayer combination reflector/electrodes were prepared bysequentially depositing approximately 700 Å chromium, approximately 500Å molybdenum and approximately 500 Å of a silver alloy containing 3percent by weight palladium on the surface of said glass element shapes.The electrochromic devices were constructed and tested in accordancewith Example 1.

[0108] The device incorporating the sequential multilayer combinationreflector electrode of chromium, molybdenum, and silver 3 percentpalladium alloy withstood CASS testing 10 times longer than devices inExample 1 before failure occurred.

EXAMPLE 4

[0109] Other than as specifically mentioned, the devices in this examplewere constructed in accordance with the conditions and teachings inExample 1. Multilayer combination reflector/electrodes were prepared bysequentially depositing approximately 700 Å chromium, approximately 500Å of a silver alloy containing 3 percent by weight palladium, andapproximately 100 Å of molybdenum on the surface of said glass elementshapes. A second set of multilayer combination reflector/electrodes werealso prepared by sequentially depositing approximately 700 Å ofchromium, approximately 500 Å molybdenum, approximately 500 Å of asilver alloy containing 3 percent by weight palladium, and approximately100 Å of molybdenum on the surface of said glass element shapes. Theelectrochromic devices were constructed and tested in accordance withExample 1.

[0110] The device incorporating the sequential multilayer combinationreflector electrode of chromium, molybdenum, silver 3 percent palladium,and molybdenum withstood steam autoclave testing 25 percent longer andCASS testing twelve times longer than the sequential multilayercombination reflector electrode device of chromium, silver 3 percentpalladium, molybdenum before failure occurred. Also, the deviceincorporating the sequential multilayer combination reflector electrodeof chromium, molybdenum, silver 3 percent palladium, molybdenumwithstood CASS testing three times longer than the device constructed inExample 3. Finally, the sequential multilayer combination reflectorelectrode device of chromium, silver 3 percent palladium, molybdenumwithstood two times longer in CASS testing and twenty times longer insteam autoclave testing than the sequential multilayer combinationreflector electrode device of chromium, silver 3 percent palladium ofExample 1.

EXAMPLE 5

[0111] Other than as specifically mentioned, the devices in this examplewere constructed in accordance with the conditions and teachings inExample 1. Multilayer combination reflector/electrodes were prepared bysequentially depositing approximately 700 Å chromium, approximately 100Å rhodium and approximately 500 Å of silver on the surface of said glasselement shapes. A second set of multilayer combinationreflector/electrodes were also prepared by sequentially depositingapproximately 700 Å of chromium, approximately 100 Å rhodium, andapproximately 500 Å of a silver alloy containing 3 percent by weightpalladium on the surface of said glass element shapes. A third set ofmultilayer combination reflector/electrodes was also prepared bysequentially depositing approximately 700 Å of chromium, approximately100 Å rhodium, and approximately 500 Å of a silver alloy containing 6percent by weight platinum on the surface of said glass element shapes.A fourth set of multilayer combination reflector/electrodes was alsoprepared by sequentially depositing approximately 700 Å of chromium,approximately 100 Å rhodium, and approximately 500 Å of a silver alloycontaining 6 percent by weight gold on the surface of said glass elementshapes. A fifth set of multilayer combination reflector/electrodes wasalso prepared by sequentially depositing approximately 700 Å ofchromium, approximately 100 Å rhodium, and approximately 500 Å of asilver alloy containing 25 percent by weight gold on the surface of saidglass element shapes. The electrochromic devices were constructed inaccordance with Example 1.

[0112] Conductive clips were connected to the offset portions of thefront and rear elements of the devices. A power source was connected tothe clips and 1.2 volts was applied to the devices continuously forapproximately 250 hours at approximately 20° C., with the connectionarranged such that the reflector/electrode was the cathode. The deviceincorporating the sequential multilayer combination reflector electrodeof chromium, rhodium, and silver exhibited a yellowing effect within theelectrochromic medium. This yellowing phenomenon was not apparent in anyof the silver alloy devices.

[0113] FIGS. 7A-7G illustrate various alternative constructions for anelectrochromic rearview mirror of the present invention, particularlywhen a light source 170, such as an information display (i.e.,compass/temperature display) or signal light, is positioned within themirror assembly behind the electrochromic mirror. According to the firstconstruction shown in FIG. 7A, the electrochromic rearview mirror wasconstructed similar to those described above, with the exception thatsecond electrode 120 includes a window 146 in the layer 121 ofreflective material in a region of second electrode 120 that is in frontof light source 170. Electrode 120 further includes a coating 172 ofelectrically conductive material that is applied over substantially allof the front surface 114 a of rear element 114. Coating 172 ispreferably at least partially transmissive so as to enable light emittedfrom light source 170 to be transmitted through the electrochromicmirror via window 146. By providing electrically conductive coating 172throughout the entire area of window 146, the electrochromic media 125in the region of window 146 will respond to the voltage applied to theclips as though window 146 was not even present. Coating 172 may be asingle layer of a transparent conductive material. Such a single layermay be made of the same materials as that of first electrode 128 (i.e.,indium tin oxide, etc.).

[0114] Transparent electrodes made of ITO or other transparentconductors have been optimized at thicknesses to maximize thetransmission of visible light (typically centered around 550 nm). Thesetransmission optimized thicknesses are either very thin layers (<300 Å)or layers optimized at what is commonly called ½ wave, full wave, 1½wave, etc. thickness. For ITO, the ½ wave thickness is about 1400 Å andthe full wave thickness is around 2800 Å. Surprisingly, thesethicknesses are not optimum for transflective (i.e., partiallytransmissive, partially reflective) electrodes with a single underlayerof a transparent conductor under a metal reflector such as silver orsilver alloys. The optimum thicknesses to achieve relative colorneutrality of reflected light are centered around ¼ wave, ¾ wave, 1¼wave, etc. optical thicknesses for light of 500 nm wavelength. In otherwords the optimal optical thickness for such a layer when underlying ametal reflector such as silver or silver alloy is mλ/4, where λ is thewavelength of light at which the layer is optimized (e.g., 500 nm) and mis an odd integer. These optimum thicknesses are ¼ wave different fromthe transmission optima for the same wavelength. Such a single layer mayhave a thickness of between 100 Å and 3500 Å and more preferably between200 Å and 250 Å, and a sheet resistivity of between about 3 Ω/□ and 300Ω/□ and preferably less than about 100 Ω/□.

[0115] Layer 121 may be made of any of the reflective materialsdescribed above and is preferably made of silver or a silver alloy. Thethickness of reflective layer 121 in the arrangement shown in FIG. 7A ispreferably between 30 Å and 800 Å. The thickness of layer 121 willdepend on the desired reflectance and transmittance properties. For aninside rearview mirror, layer 121 preferably has a reflectance of atleast 60 percent and a transmittance through window 146 of 10 to 50percent. For an outside mirror, the reflectance is preferably above 35percent and the transmittance is preferably approximately 10 to 50percent and more preferably at least 20 percent for those regions thatare in front of one of the lights of a signal light (as described inmore detail below).

[0116] Window 146 in layer 121 may be formed by masking window area 146during the application of the reflective material. At this same time,the peripheral region of the third surface may also be masked so as toprevent materials such as silver or silver alloy (when used as thereflective material) from being deposited in areas to which seal 116must adhere, so as to create a stronger bond between seal 116 andcoating 172. Additionally, an area in front of sensor 160 (FIG. 2) mayalso be masked. Alternatively, an adhesion promoting material can beadded to the seal to enhance adhesion between the seal and thesilver/silver alloy layer as described in the above-referenced U.S. Pat.No. 6,157,480.

[0117] An alternative construction to that shown in FIG. 7A is shown inFIG. 7B, where electrically conductive coating 172 is formed of aplurality of layers 174 and 176. For example, coating 172 may include afirst base layer 174 applied directly to front surface 114 a of rearelement 114, and an intermediate second layer 176 disposed on firstlayer 174. First layer 174 and second layer 176 are preferably made ofmaterials that have relatively low sheet resistivity and that are atleast partially transmissive. The materials forming layers 174 and 176may also be partially reflective. If the light emitting display behindthe partially transmissive window area 146 must be viewed often inbright ambient conditions or direct sunlight, it may be desirable tokeep the reflectivity of the window area to a minimum by using metalswith low reflectivity or other dark, black or transparent coatings thatare electrically conductive.

[0118] The material forming layer 174 should exhibit adequate bondingcharacteristics to glass or other materials of which rear element 114may be formed, while the material forming layer 176 should exhibitadequate properties so as to bond to the material of layer 174 andprovide a good bond between the applied layer 121 and seal 116. Thus,the material used for layer 174 is preferably a material selected fromthe group consisting essentially of: chromium,chromium-molybdenum-nickel alloys, nickel-iron-chromium alloys, silicon,tantalum, stainless steel, and titanium. In the most preferredembodiment, layer 174 is made of chromium. The material used to formsecond layer 176 is preferably a material selected from the groupconsisting essentially of, but not limited to: molybdenum, rhodium,nickel, tungsten, tantalum, stainless steel, gold, titanium, and alloysthereof. In the most preferred embodiment, second layer 176 is formed ofnickel, rhodium, or molybdenum. If first layer 174 is formed ofchromium, layer 174 preferably has a thickness of between 5 Å and 50 Å.If the layer of chromium is much thicker, it will not exhibit sufficienttransmittance to allow light from a light source 170, such as a displayor signal light, to be transmitted through window 146. The thickness oflayer 176 is selected based upon the material used so as to allowbetween 10 to 50 percent light transmittance through both of layers 174and 176. Thus, for a second layer 176 formed of either rhodium, nickel,or molybdenum, layer 176 is preferably between 50 Å and 150 Å. While thethicknesses of layers 174 and 176 are preferably selected to be thinenough to provide adequate transmittance, they must also be thick enoughto provide for adequate electrical conductivity so as to sufficientlyclear or darken electrochromic media 125 in the region of window 146.The coating 172 should thus have a sheet resistivity of less than 100Ω/□ and preferably less than 50 Ω/□ to 60 Ω/□.

[0119] The arrangement shown in FIG. 7B provides several advantages overthe construction shown and described with respect to FIG. 7A.Specifically, the metals used in forming coating 172 contribute to thetotal reflectance of reflector electrode 120. Accordingly, the layer ofthe reflective material 121 need not be made as thick. If, for example,silver or a silver alloy is used to form layer 121, the layer ofthickness is between 50 Å and 150 Å, thereby eliminating some of thematerial costs in providing the reflective layer. Further, the use ofreflective metals in forming coating 172 provides for a degree ofreflectance within window 146, thereby providing a much moreaesthetically pleasing appearance than if window 146 were devoid of anyreflective material whatsoever. Ideally, coating 172 provides between 30and 40 percent reflectivity in window 146. If the reflectance in window146 is too high, bright light will tend to wash out the display in thesense that it eliminates the contrast between the light of the displayand light reflecting outward from coating 172.

[0120] Another benefit of utilizing metals to form conductive coating172 is that such metals are much easier and less expensive to processthan metal oxides, such as indium tin oxide. Such metal oxides requireapplication in oxygen-rich chambers at very high temperatures, whereasmetal layers may be deposited without special oxygen chambers and atmuch lower temperatures. Thus, the process for applying multiple metallayers consumes much less energy and is much less expensive than theprocesses for forming metal oxide layers.

[0121] A third alternate arrangement for the electrochromic mirror ofthe present invention is shown in FIG. 7C. The construction shown inFIG. 7C is essentially the same as that shown in FIG. 7B except that athin silver or silver alloy layer 178 is formed on conductive coating172 within window 146. By providing only a thin layer 178 of reflectivematerial in window 146, adequate transmittance may still be providedthrough window 146 while increasing the reflectivity and electricalconductivity in that area. Layer 178 may have a thickness of between 40Å and 150 Å, whereas the layer of reflective material 121 in the otherareas may have a thickness in the order of between 200 Å and 1000 Å. Thethin layer 178 of reflective material may be formed by initially maskingthe area of window 178 while applying a portion of reflective layer 121and then removing the mask during deposition of the remainder of layer121. Conversely, a thin layer of reflective material may first bedeposited and then a mask may be applied over window 146 while theremainder of reflective layer 121 is deposited. As will be apparent tothose skilled in the art, thin layer 178 may also be formed withoutmasking by depositing reflective layer 121 to its full thickness andsubsequently removing a portion of layer 121 in the region of window146.

[0122] A modification of the configuration shown in FIG. 7C isillustrated in FIG. 7D. As will be apparent from a comparison of thedrawings, the construction of FIG. 7D only differs from that shown inFIG. 7C in that layers 174 and 176 constituting conductive coating 172are made thinner (designated as thin layers 180 and 181) in the regionof reflector/electrode 120 that is in front of light source 170. Assuch, thin layer 180 may have a thickness of between 5 Å and 50 Å,whereas layer 174 may have thicknesses anywhere between 100 Å and 1000Å. Similarly, thin layer 181 may be made of the same material as layer176 but would have a thickness of between 50 Å and 150 Å, while layer176 may have thicknesses on the order of 100 Å to 1000 Å. Thus, with theconstruction shown in FIG. 7D, the electrical conductivity,reflectivity, and transmittance within region 146 may be optimizedwithin that region while enabling the reflectance and electricalconductivity in the other regions to be optimized without concern as tothe transmittance in those areas.

[0123]FIG. 7E shows yet another alternative construction for secondelectrode 120. In the construction shown in FIG. 7E, second electrode120 includes an electrically conductive coating 172 and a reflectivecoating 178 formed over the entire third surface 114 a of the mirror. Bymaking reflective coating 178 uniformly partially transmissive, a lightsource, such as a display or signal light, may be mounted in anylocation behind the mirror and is not limited to positioning behind anyparticular window formed in second electrode 120. Again, for a rearviewmirror, second electrode 120 preferably has a reflectance of at least 35percent for an outside mirror and at least 60 percent for an insidemirror and a transmittance of preferably at least 10 percent. Conductivecoating 172 is preferably a single layer of ITO or other transparentconductive materials, but may also consist of one or more layers of thepartially reflective/partially transmissive electrically conductivematerials discussed above.

[0124] Reflective coating 178 may be constructed using a single,relatively thin, layer of a reflective electrically conductive materialsuch as silver, silver alloy, or the other reflective materialsdiscussed above. If the reflective material is silver or a silver alloy,the thickness of such a thin layer should be limited to about 500 Å orless, and a transparent conductive material, such as ITO or the like,should be utilized as electrically conductive layer 172, such thatsecond electrode 120 may have sufficient transmittance to allow adisplay or signal light to be viewed from behind the mirror. On theother hand, the thickness of the single layer of reflective materialshould be about 10 Å or more depending upon the material used to ensuresufficient reflectivity.

[0125] To illustrate the features and advantages of an electrochromicmirror constructed in accordance with the embodiment shown in FIG. 7E,ten examples are provided below. In these examples, references are madeto the spectral properties of models of electrochromic mirrorsconstructed in accordance with the parameters specified in each example.In discussing colors, it is useful to refer to the CommissionInternationale de I'Eclairage's (CIE) 1976 CIELAB Chromaticity Diagram(commonly referred to as the L a*b* chart). The technology of color isrelatively complex, but a fairly comprehensive discussion is given by F.W. Billmeyer and M. Saltzman in Principles of Color Technology, 2ndEdition, J. Wiley and Sons Inc. (1981), and the present disclosure, asit relates to color technology and terminology, generally follows thatdiscussion. On the L*a*b* chart, L* defines lightness, a* denotes thered/green value, and b* denotes the yellow/blue value. Each of theelectrochromic media has an absorption spectra at each particularvoltage that may be converted to a three number designation, theirL*a*b* values. To calculate a set of color coordinates, such as L*a*b*values, from the spectral transmission or reflectance, two additionalitems are required. One is the spectral power distribution of the sourceor illuminant. The present disclosure uses CIE Standard Illuminant A tosimulate light from automobile headlamps and uses CIE StandardIlluminant D₆₅ to simulate daylight. The second item needed is thespectral response of the observer. The present disclosure uses the 2degree CIE standard observer. The illuminant/observer combinationgenerally used for mirrors is then represented as A/2 degree and thecombination generally used for windows is represented as D₆₅/2 degree.Many of the examples below refer to a value Y from the 1931 CIE Standardsince it corresponds more closely to the spectral reflectance than L*.The value C*, which is also described below, is equal to the square rootof (a*)²+(b*)², and hence, provides a measure for quantifying colorneutrality.

[0126] It should be noted that the optical constants of materials varysomewhat with deposition method and conditions employed. Thesedifferences can have a substantial effect on the actual optical valuesand optimum thicknesses used to attain a value for a given coatingstock.

[0127] According to a first example, an electrochromic mirror wasmodeled having a back plate 114 (FIG. 7E) of glass, a layer 172 of ITOof approximately 2000 Å, a layer 178 of an alloy of silver containing 6percent gold (hereinafter referred to as 6Au94Ag) of approximately 350Å, an electrochromic fluid/gel layer 125 having a thickness ofapproximately 140 microns, a layer 128 of approximately 1400 Å of ITO,and a glass plate 112 of 2.1 mm. Using D65 illuminant at 20 degree angleof incidence, the model outputs were Y=70.7, a*=+1, and b*=+9.5. Thismodel also indicated a spectrally dependent transmittance that was 15percent over the blue-green region decreasing in the red color region ofthe spectrum to approximately 17 percent in the blue-green region of thespectrum. Elements were constructed using the values and the model astarget parameters for thickness, and the actual color, and reflectionvalues corresponded closely to those models with transmission values ofapproximately 15 percent in the blue and green region. In this example,1400 Å ITO (½ wave) would produce a far more yellow element (b* ofapproximately 18).

[0128] Typically, thin silver or silver alloy layers are higher inblue-green transmission and lower in blue-green light reflection whichimparts a yellow hue to the reflected image. The 2000 Å ITO underlayerof approximately ¾ wave in thickness supplements the reflection ofblue-green light which results in a more neutral hue in reflection.Other odd quarter wave multiples (i.e., ¼, {fraction (5/4)}, {fraction(7/4)}, etc.) are also effective in reducing reflected color hue. Itshould be noted that other transparent coatings, such as (F)SnO or(AL)ZnO, or a combination of dielectric, semi-conductive, or conductivecoatings, can be used to supplement blue-green reflection and produce amore neutral reflected hue in the same manner.

[0129] According to a second example of the embodiment illustrated inFIG. 7E, an electrochromic mirror was modeled having a back plate 114 ofglass, layer 172 including a sublayer of titanium dioxide ofapproximately 441 Å and a sublayer of ITO of 200 Å, a layer 178 of6Au94Ag of approximately 337 Å, an electrochromic fluid/gel 125 having athickness of approximately 140 microns, a layer 128 of approximately1400 Å of ITO, and a glass plate 112 of 2.1 mm. In air, the model of theconductive thin film 120 on glass 114 for this example, using D65illuminant at 20 degree angle of incidence, exhibited values ofapproximately Y=82.3, a*=0.3, and b*=4.11. This model also indicated arelatively broad and uniform transmittance of 10-15 percent across mostof the visible spectrum, making it an advantageous design for aninterior rearview mirror with a multi-colored display or a white lightdisplay or illuminator. When this back plate system 114, 120 isincorporated into an electrochromic mirror, the predicted overallreflectance decreases and the transmittance increases.

[0130] According to a third example of an electrochromic mirrorconstructed as shown in FIG. 7E, an electrochromic mirror was modeledhaving a back plate 114 of glass, a layer 172 including a sublayer oftitanium dioxide of approximately 407 Å and a sublayer of ITO of 200 Å,a layer 178 of 6Au94Ag of approximately 237 Å, an electrochromicfluid/gel layer 125 having a thickness of approximately 140 microns, alayer 128 of approximately 1400 Å of ITO, and a glass plate 112 of 2.1mm. In air, the model of the conductive thin film 120 on glass 114, forthis example, using D65 illuminant at 20 degree angle of incidence,exhibited values of approximately Y=68.9, a*=0.03, and b*=1.9. Thismodel also indicated a relatively broad and uniform transmittance ofapproximately 25 to 28 percent across most of the visible spectrum,making it an advantageous design for an exterior rearview mirror with amulti-color display or a white light display or illuminator. When thisback plate system 114, 120 is incorporated into an electrochromicmirror, the predicted overall reflectance decreases and thetransmittance increases.

[0131] According to a fourth example of the embodiment shown in FIG. 7E,an electrochromic mirror was modeled having a back plate 114 of glass, alayer 172 including a sublayer of titanium dioxide of approximately 450Å and a sublayer of ITO of 1600 Å, a layer 178 of 6Au94Ag ofapproximately 340 Å, an electrochromic fluid/gel layer 125 having athickness of approximately 140 microns, a layer 128 of approximately1400 Å of ITO, and a glass plate 112 of 2.1 mm. In air, the model of theconductive thin film 120 on glass 114, for this example, using D65illuminant at 20 degree angle of incidence, exhibited values ofapproximately Y=80.3, a*=−3.45, and b*=5.27. This model also indicated arelative transmittance peak at about 600 nm of approximately 17 percent.When this back plate system 114, 120 is incorporated into anelectrochromic mirror, the predicted overall reflectance decreases andthe transmittance increases. As one compares this stack to the secondexample, it illustrates, in part, a principle of repeating optima in theprimarily transmissive layer or layers (e.g., layer 172) of thesedesigns as one increases their thickness or thicknesses. The optima willbe determined by several factors which will include good colorneutrality, reflection, and transmission.

[0132] According to a fifth example of the embodiment shown in FIG. 7E,an electrochromic mirror was modeled having a back plate 114 of glass; alayer 172 including a sublayer of titanium dioxide of approximately 450Å, a sublayer of ITO of 800 Å, a sublayer of silica of 50 Å, and anadditional sublayer of ITO of 800 Å; a layer 178 of 6Au94Ag ofapproximately 340 Å; an electrochromic fluid/gel layer 125 having athickness of approximately 140 microns, a layer 128 of approximately1400 Å of ITO; and a glass plate 112 of 2.1 mm. In air, the model of theconductive thin film 120 on glass 114, for this example, using D65illuminant at 20 degree angle of incidence, exhibited values ofapproximately Y=80.63, a*=−4.31, and b*=6.44. This model also indicateda relative transmittance peak at about 600 nm of approximately 17percent. When this back plate system is incorporated into anelectrochromic mirror, the predicted overall reflectance decreases andthe transmittance increases. This stack also demonstrates, in part, aprinciple of a flash layer incorporation in these designs. In thisparticular case, the 50 Å silica layer does not contribute substantiallyto the design when compared to the fourth example, nor does it detractfrom it greatly. The insertion of such layers would not, in the opinionof the inventors, circumvent any claims that might depend on the numberof layers or the relative refractive indices of layer sets. Flash layershave been shown to impart substantial advantages when used over layer178 and are discussed above. It is also believed that such flash layerscould have adhesion promotion or corrosion resistance advantages whenpositioned between layers 172 and 178 as well as between glass 114 andlayer(s) 120, especially when comprised of metal/alloys mentioned aboveas having such functions in thicker layers.

[0133] According to a sixth example of the embodiment shown in FIG. 7E,an electrochromic mirror was modeled having a back plate 114 of glass, alayer 172 including a sublayer of titanium dioxide of approximately 450Å and a sublayer of ITO of 1600 Å, a layer 178 of silver of 290 Å and aflash layer of 6Au94Ag of approximately 50 Å, an electrochromicfluid/gel layer 125 having a thickness of approximately 140 microns, alayer 128 of approximately 1400 Å of ITO, and a glass plate 112 of 2.1mm. In air, on glass 114, the model of the conductive thin film 120 forthis example, using D65 illuminant at 20 degree angle of incidence,exhibited values of approximately Y=81.3, a*=−3.26, and b*=4.16. Thismodel also indicated a relative transmittance peak at about 600 nm ofabout 17 percent. When this back plate system 114, 120 is incorporatedinto an electrochromic mirror, the predicted overall reflectancedecreases and the transmittance increases. As one compares this stack tothe fourth example, it illustrates, in part, the principle of using aflash layer of a silver alloy over silver. The potential advantages ofsuch a system for layer 178, as opposed to a single alloy layer per thefourth example, include, but are not limited to, reduced cost, increasedreflectivity at the same transmission or increased transmissivity at thesame reflectance, decreased sheet resistance, and the possibility ofusing a higher percentage of alloyed material in the flash overcoatlayer to maintain enhanced electrode surface properties the silver alloyexhibits over pure silver. Similar potential advantages apply to thecases of different percentage alloys or a graded percentage alloy inlayer 178.

[0134] According to a seventh example of the embodiment shown in FIG.7E, an electrochromic mirror was modeled having a back plate 114 ofglass, a layer 172 of silicon of approximately 180 Å, a layer 178 of6Au94Ag of approximately 410 Å, an electrochromic fluid/gel layer 125having a thickness of approximately 140 microns, a layer 128 ofapproximately 1400 Å of ITO, a glass plate 112 of 2.1 mm. In air, onglass 114, the model of the conductive thin film 120 for this example,using D65 illuminant at 20 degree angle of incidence, exhibited valuesof Y=80.4, a*=0.9, and b*=−3.39. In contrast, a thin layer of 6Au94Ag onglass with similar reflectivity exhibits a yellow hue in reflection. Themodel also indicated a spectrally dependent transmittance that reached apeak of about 18 percent at 580 nm. When this back plate system 114, 120is incorporated into an electrochromic mirror, the predicted overallreflectance and the transmittance increases. In this case, the valueswould be appropriate for an automotive interior transflective mirror.This system would be especially useful if the silicon were deposited asa semi-conductive material, thereby allowing for masking of the silveralloy layer so that the silver alloy would be deposited primarily in theviewing area while still maintaining conductivity to the area to bedarkened.

[0135] According to an eighth example of the embodiment shown in FIG.7E, an electrochromic rearview mirror was modeled having a back plate114 of glass, a layer 172 including a sublayer of silicon ofapproximately 111 Å and a sublayer of ITO of approximately 200 Å, alayer 178 of 6Au94Ag of approximately 340 Å, an electrochromic fluid/gellayer 125 having a thickness of approximately 140 microns, a layer 128of approximately 1400 Å of ITO, and a glass plate 112 of 2.1 mm. In air,on glass 114, the model of the conductive thin film 120 for this exampleusing D65 illuminant at 20 degree angle of incidence exhibited values ofapproximately Y=80.7, a*=0.1, and b*=−1.7. The model also indicated aspectrally dependent transmittance that reached a peak at about 18percent at 600 nm. When this back plate system 114, 120 is incorporatedinto an electrochromic mirror, the predicted overall reflectancedecreases and the transmittance increases. In this case, the valueswould be appropriate for an automotive transflective mirror. Also inthis case, masking of the silver alloy layer could take place in theseal area, and the conductivity of the back electrode of the systemwould be maintained by the ITO layer whether or not the silicon weresemi-conductive. This example is advantageous in that it utilizes thinlayers, which are easier to form during high volume manufacturing.

[0136] According to a ninth example of the embodiment shown in FIG. 7E,an electrochromic mirror was modeled having a back plate 114 of glass, alayer 172 including a sublayer of silicon of approximately 77 Å and asublayer of ITO of approximately 200 Å, a layer 178 of 6Au94Ag ofapproximately 181 Å, an electrochromic fluid/gel layer 125 having athickness of approximately 140 microns, a layer 128 of approximately1400 Å of ITO, and a glass plate 112 of 2.1 mm. In air, on glass, themodel of the conductive thin film 120 for this example, using D65illuminant at 20 degree angle of incidence, exhibited values ofapproximately Y=64.98, a*=1.73, and b*=−2.69. The model also indicated aspectrally dependent transmittance that reached a peak of about 35percent at 650 nm. When this back plate system is incorporated into anelectrochromic mirror, the predicted overall reflectance decreases andthe transmittance increases. In this case, the values would beappropriate for an automotive exterior transflective mirror.

[0137] According to a tenth example of the embodiment shown in FIG. 7E,an electrochromic mirror was modeled having a back plate 114 of glass, alayer 172 of fluorine-doped tin oxide of approximately 1957 Å (¾ waveoptima thickness), a layer 178 of 6Au94Ag of approximately 350 Å, anelectrochromic fluid/gel layer 125 having a thickness of approximately140 microns, a layer 128 of approximately 1400 Å of ITO, and a glassplate 112 of 2.1 mm. In air, on glass 114, the model of the conductivethin film 120, for this example, using D65 illuminant at 20 degree angleof incidence, exhibited outputs of approximately Y=80.38, a*=1.04, andb*=5.6. The model also indicated a spectrally dependent transmittancethat overall diminished as wavelength increased in the visible range.Transmittance at 630 nm was predicted as approximately 10 percent. Whenthis back plate system is incorporated into an electrochromic mirror,the predicted overall reflectance decreases and the transmittanceincreases. In this case, the values would be appropriate for anautomotive interior transflective mirror.

[0138] In a mirror construction, such as that shown in FIG. 7E, themirror preferably exhibits a reflectivity of at least 35 percent, morepreferably at least 50 percent, and more preferably at least 65 percentfor an outside mirror and, for an inside mirror, the mirror preferablyexhibits a reflectance of at least 70 percent and more preferably atleast 80 percent. To obtain such reflectance levels, the reflectivesecond electrode 120 should have a slightly higher reflectance. Themirror preferably exhibits a transmittance of at least about 5 percent,more preferably at least about 10 percent, and most preferably at leastabout 15 percent. To obtain these transmittance levels, the secondelectrode 120 may have a slightly lower transmittance.

[0139] Because electrochromic mirrors having a b* value of greater than+15 have an objectionable yellowish hue, it is preferable that themirror exhibits a b* value less than about 15, and more preferably lessthan about 10. Thus, second electrode 120 preferably exhibits similarproperties.

[0140] To obtain an electrochromic mirror having relative colorneutrality, the C* value of the mirror should be less than 20.Preferably, the C* value is less than 15, and more preferably is lessthan about 10. Second electrode 120 preferably exhibits similar C*values.

[0141] The inventors have recognized that, when a thin layer of silveror silver alloy is used in a rearview mirror such as those describedabove, the thin layer may impart a light yellow hue (b* greater than+15) to objects viewed in the reflection particularly when the thinlayer of silver or silver alloy is made thin enough to impart sufficienttransmittance of 5 percent or more. This causes the mirror to no longerappear color neutral (C* greater than 20). Conversely, transmissionthrough the film is higher for blue light than for red light. The tenpreceding examples compensate for this liability by selection of theappropriate thicknesses of various underlayer films. Another approach tominimizing the yellow hue of the reflected images is to reflect thetransmitted blue light back through the mirror. Typically, in the priorart signal or display mirrors a coating of black paint is applied to thefourth surface of the mirror in all areas except for where a display ismounted (if one is employed). Such a black coating was designed toabsorb any light that is transmitted through the mirror and itsreflective layer(s). To minimize the yellow hue of the reflected imageappearing when a thin silver/silver alloy material is used, the blackcoating may be replaced with a coating 182 that reflects the blue lightback through the mirror rather than absorbing such blue light.Preferably, blue paint is used in place of the black paint since theblue backing reflects blue light. Alternatively, coating 182 may bewhite, gray, or a reflective coating such as chrome, since they toowould reflect blue light back through the reflective layer(s) and theremainder of the mirror.

[0142] To demonstrate the effectiveness of blue coating 182 on thefourth surface 114 b of a mirror, an electrochromic mirror wasconstructed with a thin layer of silver 178 over a 100 Ω/□ ITO layer 172as the third surface reflector/electrode 120. The white lightreflectivity of the mirror was about 52 percent, and the white lighttransmission was about 30 percent. The mirror had a noticeably yellowhue in reflection and a blue hue in transmission. The mirror was placedon a black background and the color was measured using a SP-68Spectrophotometer from X-Rite, Inc. of Grandville, Mich. The measured b*value was +18.72. The same mirror was then placed on a blue backgroundand the color was again measured. With the blue background, the measuredb* value fell to +7.55. The mirror thus exhibited noticeably less yellowhue in reflection on the blue background as compared to a blackbackground.

[0143] Yet another variation of reflector/electrode 120 is illustratedin FIG. 7F. As illustrated, reflector/electrode 120 is constructedacross substantially the entire front surface 114 a of rear element 114with an electrically conductive multi-layer interferential thin-filmcoating 190. Conductive thin-film coating 190 is preferably tailored tomaximize transmittance to light having wavelengths within a narrow bandcorresponding to the wavelength of light emitted from light source 170.Thus, if light source 170 were a signal light including red, red-orange,or amber AlGaAs or AlInGaP LEDs, the light emitted from such LEDs wouldhave wavelengths in the range of 585 nm to 660 nm, and conductivethin-film coating 190 would be tailored to maximize spectraltransmittance at those wavelengths. By increasing the transmittancepreferentially within this relatively narrow band of wavelengths, theaverage luminous reflectance to white light remains relatively high. Aswill be apparent from the four examples provided below of electrodesconstructed using such conductive thin-film coatings, the conductivethin-film coating as so constructed includes a first layer 184 of afirst material having a relatively high refractive index, a second layer186 of a second material formed on first layer 184 where the secondmaterial has a relatively low refractive index, and a third layer 187formed on second layer 186 and made of a material that has a relativelyhigh refractive index. Conductive thin-film coating 190 may also includea thin fourth layer 188 of an electrically conductive material formed onthird layer 187. If third layer 187 is not electrically conductive,fourth layer 188 of an electrically conductive material must be disposedon third layer 187. If the first, second, and third layers providesufficient reflectivity, such a fourth layer 188 may be made of atransparent conductive material. If not, fourth layer 188 may be made ofa reflective material.

[0144] Conductive thin-film coating 190 preferably exhibits: a luminousreflectance of 35 to 95 percent, a reflected C* value of 20 or less, asignal light/display luminous transmittance of 10 percent or more, and asheet resistance of less than 100 Ω/□. More preferably, C* is less than15 and most preferably less than 10, and the value of a* is negative. Asa measure of comparison, luminous reflection and reflected C* for thiscoating may be measured using one or more of the CIE illuminants A, B,C, or D55, D65, an equal-energy white source or other broad-band sourcemeeting the SAE definition of white. Luminous reflectance and reflectedC* for this coating may be measured at one or more angles of incidencebetween 10° and 45° from the surface normal. The signal light/displayluminous transmittance for this coating may be measured using one ormore signal or display sources such as amber, orange, red-orange, red,or deep red LEDs, vacuum fluorescent displays (VFDs), or other lamps ordisplays, and at one or more angles of incidence between 20° and 55°from the surface normal. As will be apparent to those skilled in theart, “Luminous Reflectance” and “Signal light/display LuminousTransmittance” imply use of either or both of the 1931 CIE 2 degreeobserver V_(λ) or V_(λ)′ as the eye-weighting functions.

[0145] By configuring conductive thin-film coating 190 to have areflectance, transmittance, electrical conductivity, and a reflected C*value within the above parameters, an electrode may thus be constructedthat has medium to high reflectance, substantially neutral reflectancefor faithful rendering, medium to high in-band signal light/displaytransmittance for efficiency and brightness, and low sheet resistancefor good electrochromic functionality.

[0146] In the specific examples of such a conductive thin-film coating,the first and third materials forming first and third layers 184 and187, respectively, may be the same or a different material selected fromthe group consisting essentially of indium tin oxide, fluorine-doped tinoxide, titanium dioxide, tin dioxide, tantalum pentoxide, zinc oxide,zirconium oxide, iron oxide, silicon, or any other material having arelatively high refractive index. Second layer 186 may be made ofsilicon dioxide, niobium oxide, magnesium fluoride, aluminum oxide, orany other material having a low refractive index. First layer 184 mayhave a thickness of between about 200 Å to 800 Å, second layer 186 mayhave a thickness of between about 400 Å to 1200 Å, third layer 187 mayhave a thickness between about 600 Å to 1400 Å, and layer 188 may have athickness of about 150 Å to 300 Å. Other optima thicknesses outsidethese ranges may also be obtainable per the above description. Insertingadditional layer sets of low and high index materials can raisereflectance further. Preferably, the electrically conductive materialforming fourth layer 188 is made of a reflective material such as silveror silver alloy, or of a transparent conductive material such as ITO.

[0147] According to a first example of conductive thin-film coating 190,an electrochromic mirror was modeled having a front element 112 having athickness of 2.2 mm, a first electrode 128 made of ITO and having athickness of approximately 1400 Å, an electrochromic fluid/gel having athickness of approximately 137 to 190 microns, and a conductivethin-film coating 190 provided on a rear glass substrate 114. Conductivethin-film coating 190 in this first example included a first layer 184made of ITO and having a thickness of approximately 750 Å, a secondlayer 186 made of SiO₂ and having a thickness of approximately 940 Å, athird layer 187 made of ITO and having a thickness of approximately 845Å, and a fourth layer 188 made of silver and having a thickness of 275Å. In air, the conductive thin-film coating 190 modeled in this firstexample exhibited a luminous reflectance of approximately 80.2 percentfor white light and a spectral transmittance of approximately 22.5percent on average for light having wavelengths between 620 nm and 650nm. Such characteristics make the conductive thin-film coating 190according to this first example suitable for use either in an inside oroutside rearview mirror. When this conductive thin-film coating isapplied to the front surface of rear glass element and incorporated intoan electrochromic mirror, the overall reflectance decreases and thetransmittance increases.

[0148] According to a second example, another electrochromic mirror wasmodeled having the same features as discussed above with the exceptionthat conductive thin-film coating 190 included a first layer 184 made ofITO and having a thickness of approximately 525 Å, a second layer ofSiO₂ having a thickness of approximately 890 Å, a third layer 187 madeof ITO and having a thickness of approximately 944 Å, and a fourth layer188 made of silver and having a thickness of approximately 168 Å. Inair, the conductive thin-film coating as constructed in the secondexample has a luminous reflectance of approximately 63 percent for whitelight incident thereupon at a 20° angle of incidence, and a spectraltransmittance of approximately 41 percent on average for light havingwavelengths in the 620 nm to 650 nm wavelength range at 20° angle ofincidence. Such a conductive thin-film coating 190 is particularlysuitable for an outside rearview mirror. When this conductive thin-filmcoating is applied to the front surface of rear glass element andincorporated into an electrochromic mirror, the overall reflectancedecreases and the transmittance increases.

[0149] A conductive thin-film coating according to a third example wasmodeled that was made of the same materials as described for the firsttwo conductive thin-film coatings except that first layer 184 had athickness of approximately 525 Å, second layer 186 had a thickness ofapproximately 890 Å, third layer 187 had a thickness of approximately945 Å, and fourth layer 188 had a thickness of approximately 170 Å. Inair, the conductive thin-film coating thus modeled had a luminousreflectance of 63 percent at 20° angle of incidence for illuminationwith white light, and an average spectral transmittance of approximately41 percent for light having wavelengths between the 620 nm and 650 nmwavelength range at 200 angle of incidence. When this conductivethin-film coating is applied to the front surface of rear glass elementand incorporated into an electrochromic mirror, the overall reflectancedecreases and the transmittance increases.

[0150] According to a fourth example, a non-conductive three layerinterference coating available from Libbey Owens Ford (LOF) of Toledo,Ohio, is used in combination with a conductive fourth layer 188 of ITOor the like. The thin film stack available from LOF has a first layer184 of Si, a second layer 186 of SiO₂, and a third layer 187 of SnO₂.This coating has a reflectance of approximately 80 percent and atransmittance of approximately 4 percent for white light, andtransmittance of 7 to 10 percent for light having wavelengths in the 650to 700 nm range. The transmittance in the 650 to 700 nm range makes thisthin film stack particularly suitable for a signal mirror that utilizesa red light source. While the SnO₂, SiO₂ and Si used in the LOF thinfilm stack are not highly reflective materials by themselves(particularly when applied as a thin layer), the alternating layers ofsuch materials having high and low refractive indices produce therequisite high level of reflectivity. The poor electrical conductivityof this thin film stack requires that it be implemented with anelectrically conductive layer that has good electrical conductivity,such as a layer of ITO or the like. The LOF thin film stack overcoatedwith an ITO layer having a half-wave thickness exhibited a sheetresistance of 12 Ω/□. When the ITO/LOF thin-film stack was used as asecond electrode for an electrochromic mirror, the mirror had areflectance of 65 percent. Several different displays were placed behindthe assembled mirror and were all easily observed.

[0151]FIG. 7G shows yet another alternate construction that is verysimilar to that shown in FIG. 7F, with the exception that only threelayers are utilized for the electrically conductive multi-layerthin-film coating 190. According to the construction shown in FIG. 7G,thin-film coating 190 includes a first layer 184 made of a materialhaving a high refractive index such as the materials noted above inconnection with FIG. 7F, a second layer made of a material having a lowrefractive index such as those materials also discussed above for layer186 in FIG. 7F, and a third layer 188 of electrically conductivematerial. Layer 188 need not be made of a material having a highrefractive index, but rather may be made of any electrically conductivematerial suitable for use in an electrochromic mirror. For example,layer 188 may be a highly reflective metal, such as silver or a silveralloy, or may be a metal oxide, such as ITO. To illustrate thefeasibility of such a coating, two examples are described below.

[0152] In a first example, an electrochromic mirror was modeled having afirst layer 184 of ITO deposited on a front surface of rear glasssubstrate 114 at a thickness of 590 Å, a second layer 186 of silicondioxide applied at a thickness of 324 Å over first layer 184, and athird layer 188 of silver having a thickness of 160 Å applied oversecond layer 186. The electrochromic mirror was then illuminated with aCIE illuminant D65 white light source at an angle of incidence of 20°.When illuminated with such white light, the mirror exhibited a luminancereflectance of 52 percent and a* and b* values of approximately 1.0 and5.0, respectively. When illuminated with a red LED source at 35° angleof incidence, the mirror exhibited a luminous transmittance of 40percent.

[0153] According to a second example of the structure shown in FIG. 7G,an electrochromic mirror was modeled having a first layer 184 of silicondeposited at a thickness of 184 Å on the front surface of glasssubstrate 114, a second layer 186 deposited on first layer 184 andformed of silicon dioxide at a thickness of 1147 Å, and a third layer188 of ITO of a thickness of 1076 Å applied over second layer 186. Theelectrochromic mirror having such a coating was illuminated with a CIEilluminant D65 white light source at 20° angle of incidence. Whenmodeled as illuminated with such white light, the modeled mirrorexhibited a luminous reflectance of 54 percent and a* and b* values of−2.5 and 3.0, respectively. When modeled as illuminated with a red LEDsource at 35° angle of incidence, the modeled mirror exhibited aluminous transmittance of approximately 40 percent.

[0154] Considering that the above two three-layer examples exhibitedluminous reflectance in excess of 50 percent and transmittance ofapproximately 40 percent, a mirror constructed as shown in FIG. 7G meetsthe specific objectives noted above with respect to FIG. 7F, and istherefore suitable for use in an outside electrochromic rearview mirrorincorporating a signal light.

[0155] As will be apparent to those skilled in the art, the electricallyconductive multi-layer thin-film coating described above may beimplemented as a third surface reflector for an electrochromic mirrorregardless of whether the electrochromic medium is a solution-phase,gel-phase, or hybrid (solid state/solution or solid state/gel).

[0156] Although the above alternative constructions shown and describedwith respect to FIGS. 7A-7G do not include a flash-over protective layersuch as layer 124 shown in FIG. 3, those skilled in the art willunderstand that such a flash-over layer may be applied over any of thevarious reflector/electrode 120 constructions shown in FIGS. 7A-7G.

[0157]FIG. 8 shows a cross section of one embodiment of the presentinvention as similarly illustrated in FIG. 7E above. Specifically, bymounting a light emitting display assembly, indicator, enunciator, orother graphics 170 behind a reflective layer such as layer 178, spuriousreflections occur at various interfaces within the electrochromic mirrorthat result in one or more ghost images being readily viewable by thevehicle occupants. The perceived separation between these imagesincreases as the reflective surfaces move further apart. In general, thethinner the glass used in the mirror construction, the lessobjectionable the images become. However, eliminating or reducing theintensity of the spurious reflections enhances the overall clarity ofthe display. As shown in FIG. 8, a point of illumination from display170 emits light through element 114 as illustrated by light rays A andB, which are only two of an infinite number of light rays that could betraced from any one point source. Light rays A and B are thentransmitted through transparent conductive layer 172 with little or noreflections at the interface between electrode 172 and element 114 dueto the closeness of the indices of refraction of these two components.The light then reaches the interface between transparent layer 172 andreflective layer 178, where between 10 and 20 percent of the light istransmitted through reflective layer 178 into electrochromic medium 125.A large percentage of the light intensity striking reflective layer 178is thus reflected back as illustrated by light rays C and D. Whilereflected light that is incident upon a paint layer 182 on rear surface114 b of element 114 (ray C) may be absorbed substantially in itsentirety, light that is reflected back at display 170 (ray D) is notabsorbed by the layer of absorbent paint 182. Because many lightemitting displays, such as a vacuum fluorescent display with a glass topplate, an LCD, or any other display assembly mounted such that there isan air gap between surface 114 b and the front surface of display 170,typically include at least one specular surface 171, light reflectedback at the specular surface(s) 171 of display 170 (ray D) is reflectedoff surface 171 back through element 114, reflective electrode 120,electrochromic medium 125, layers 128 and 130, and element 112. Thisspurious reflection off the specular surface 171 of display 170 thuscreates a ghost image that is viewable by the vehicle occupants.Additional spurious reflections occur at the outer surface 112 a ofelement 112 due to the differences in refractive indices of element 112and the air surrounding the electrochromic mirror. Thus, lightrepresented by ray F is reflected back into the mirror from surface 112a and is subsequently reflected off of reflective layer 178 back thoughmedium 125, layers 128 and 130, and element 112. It is thereforedesirable to implement various measures that eliminate or reduce theintensity of these spurious reflections and thereby eliminate theannoying ghost images that are visible to the vehicle occupants. FIGS.9A-9D, which are described below, illustrate various modifications thatmay be made to reduce these spurious reflections. It should be notedthat these spurious reflections are always lower in brightness than thenonreflected image. One approach to improving the clarity of the displaywithout eliminating spurious reflections is to control the displaybrightness such that the intensity of the secondary images are below thevisual perception threshold. This brightness level will vary withambient light levels. The ambient light levels can be accuratelydetermined by photosensors in the mirror. This feedback can be used toadjust the display brightness so the secondary images are not brightenough to be objectionable.

[0158] In the embodiment shown in FIG. 9A, means 192 and 194 areprovided for reducing or preventing reflections from specular surface171 and front surface 112 a of element 112, respectively.Anti-reflective means 192 may include an anti-reflective film applied tothe rear surface 114 b of element 114 or to any and all specularlyreflecting surfaces of display assembly 170. Anti-reflective means 192may also include a light absorbing mask applied to rear surface 1114 bor specular surface 171 of display assembly 170. Such a masking layer192 may be made to cover substantially the entirety of specular surface171, with the exception of those regions lying directly over a lightemitting segment of display 170. The masking may be made with any lightabsorbing material, such as black paint, black tape, black foam backing,or the like. It should be noted that vacuum florescent displays areavailable with an internal black mask in all areas around the individuallight emitting elements. If anti-reflective means 192 is formed as ananti-reflective layer, substantially any known anti-reflective film maybe employed for this purpose. The anti-reflective film need only beconstructed to prevent reflections at the particular wavelength of thelight emitted from display 170.

[0159] By providing anti-reflective means 192 as described above, anylight that is reflected back from reflective layer 178 toward specularsurface 171 of display 170 is either absorbed or transmitted intodisplay 170, such that it cannot be reflected from surface 171 throughthe device towards the eyes of the vehicle occupants. It should be notedthat anti-reflective means 192 may also include any other structurecapable of reducing or preventing the reflection of light from specularsurface 171. Further, anti-reflective means 192 may include acombination of an anti-reflective film and a masking layer and layer 192may be incorporated on any specularly reflective surface that couldreflect light reflected off reflector 178, for example, either the backsurface of glass element 114, the front surface of display 170, or anyinternal surface in display 170.

[0160] To reduce the spurious reflections from the air interface withsurface 112 a of element 112, an anti-reflective film 194 may beprovided on surface 112 a. Anti-reflective film 194 may be formed of anyconventional structure. A circular polarizer inserted between thetransflective coating and the display is also useful in reducingspurious reflections.

[0161]FIG. 9B shows an alternative solution to the problems relating tothe reflection of light from display 170 off reflective layer 178 andthe specular surface of the display. Specifically, display 170 ispreferably selected from those displays that do not include any form ofspecular surface. Examples of such displays are available from HewlettPackard and are referenced as the HDSP Series. Such displays generallyhave a front surface that is substantially light absorbing, such thatlittle if any light would be reflected off the forward-facing surface ofthe display.

[0162] Another example of a display construction that would not have aspecularly reflecting surface (such as between glass and air) would be aback lit liquid crystal display (LCD) that is laminated directly ontothe back mirror surface 114 b to eliminate the air gap or air interfacebetween the display and the mirror. Eliminating the air gap is aneffective means of minimizing the first surface reflection of alldisplay devices. If the type of LCD used was normally opaque or darksuch as with a twisted nematic LCD with parallel polarizers or a phasechange or guest host LCD with a black dye, the reflected light would beabsorbed by the display and not re-reflected back toward the viewer.Another approach would be to use a back lit transmissive twisted nematicLCD with crossed polarizers. The entire display area would then beilluminated and contrasted with black digits. Alternatively, a positiveor negative contrast electrochromic display could be used in place ofthe LCD, or an organic LED could be laminated or fixed to the backsurface 114 b.

[0163] An alternative solution is shown in FIG. 9C, whereby display 170is mounted in back of rear surface 114 b of rear element 114, such thatspecular surface 171 is inclined at an angle to rear surface 114 b. Asapparent from the ray tracings in FIG. 9C, any light emitted fromdisplay 170 that reflects off of reflective layer 178 back towardspecular surface 171 of display 170 is reflected off of specular surface171 at an angle which could direct the light beam away from the viewertowards, for instance, the roof of the vehicle or, if the angle of thedisplay is great enough, the beam could be directed toward an absorbingsurface such as a black mask applied to the back of the mirror onsurface 114 b. It should be noted that, rather than angling the display,the reflected beam could be deflected by some other means such as bylaminating a transparent wedge shape on the front of the display, thegoal being to redirect the reflected light out of the viewing cone ofthe display or to an absorbing media or surface.

[0164] As shown in FIG. 9E, another useful technique to reduce spuriousreflections is to reflect the display image off of a mirror surface 197(preferably a first surface mirror) at about a 45° angle and thenthrough the transflective layer 120. The image reflected off thetransflective layer 120 can then be redirected away from the specularsurfaces on the display by slightly angling the relationship of thedisplay to the transflective layer.

[0165]FIG. 9D shows yet another approach for overcoming the problemsnoted above. Specifically, the embodiment shown in FIG. 9D overcomes theproblem by actually mounting the display in front of reflective layer178. To enable the display to be mounted in front of the reflectedlayer, a substantially transparent display, such as an organic lightemitting diode (OLED) 196 is utilized. OLEDs are available fromUniversal Display Corporation. Such OLEDs can be constructed such thatthey are thin transparent displays that could be mounted inside thechamber in which the electrochromic medium is maintained. Because OLED196 can be transparent, it would not interfere with the image viewed bythe driver of the vehicle. Additionally, by providing OLED 196 insidethe chamber between the substrates, display 196 is protected from anyadverse environmental effects. Thus, such an arrangement is particularlydesirable when mounting a display device in an exterior automotiverearview mirror. OLED 196 could be mounted on layer 178, layer 128,between layers 128 and 130, between layer 130 and element 112, betweenlayers 172 and 178, between layer 172 and element 114, to rear surface114 b of element 114, or to surface 112 a of element 112. Preferably,OLED display 196 is mounted in front of reflective layer 178 in thechamber between elements 112 and 114.

[0166] To take advantage of the fact that the reflective layer in anelectrochromic mirror may be partially transmissive over its entiresurface area, a light collector may be employed behind the reflectivelayer to collect the light impinging on the mirror over a much largerarea than previously possible and to amplify the light as it is directedonto a photosensor. As will be described in more detail below, the useof such a light collector more than compensates for the lack of theprovision of an opening in the reflective layer and actually canincrease the sensitivity of the glare sensor in an electrochromicmirror.

[0167]FIG. 10 is a front view of an inside rearview mirror constructedin accordance with the present invention. FIG. 11 is a cross-sectionalview taken along plane 11-11′ of FIG. 10. According to thisconstruction, the light collector may be constructed as a plano-convexlens 609 mounted behind a partially transmissive reflecting surface 607and a variable attenuating layer 608. As shown in FIG. 11, lens 609projects light from source 601 onto focal point 604 and light fromsource 601 a onto focal point 604 a. A small area sensor, for example,the single pixel sensor of U.S. patent application Ser. No. 09/237,107,filed on Jan. 25, 1999, now abandoned, which is incorporated herein byreference, is provided to sense glare from the rear viewed through lens609, partially transmissive layer 607, and optionally through variableattenuating layer 608. This construction takes advantage of the factthat the active sensing area of sensor 605 is small, for example, 100microns on a side, and that a relatively large light collector, lens 609in this example, can be substantially hidden behind the partiallytransmissive mirror and configured so that relatively high optical gainmay be provided for the sensor while still providing a characterized andrelatively large field of view over which glare is sensed. In theexample shown in FIG. 11, light source 601 a is approximately 20 degreesoff the central axis and is close to the edge of the amplified field ofview. Note that unamplified light, part of which may not pass throughthe lens, may be used to maintain some sensitivity to glare over alarger field of view.

[0168] When designing a construction such as those shown in FIGS. 10 and11, there are several design considerations. Because the source of lightthat impinges upon the mirror and creates glare is the head lamps ofautomobiles to the rear of the vehicle, and such light sources are at agreat distance away from the mirror relative to the size of the lens,the rays from an automotive head lamp light source are substantiallyparallel. With a good lens, most of the rays impinging on the lens froma source are projected to a relatively small, intense spot at the focalpoint 604. For a sensing position other than at the focal point, as afirst approximation, the optical gain is the ratio of the area of thelens through which light enters to that of the cross section of thefocussed cone in the plane where the light is sensed. In FIG. 11, with aspherical or aspherical lens 609, this would be the square of the ratioat the diameter of lens 609 to the length of line 610. This isapproximately 10 as depicted. If sensor 605 was placed at the focalpoint 604 as it would be if it were a pixel in an imaging array, nearlyall of the light passing through the lens from light source 601 wouldstrike sensor 605, making the optical gain very high. However, lightfrom a light source 601 a would totally miss the sensor and the field ofview would be extremely small. In FIG. 11, sensor 605 is placed at ahighly de-focussed point, which is common to the cones of light fromlight sources having positions for which optical gain should bemaintained. Note that the plane can optionally be chosen beyond thefocal point or other methods of diffusion may be used alone or incombination to widen and characterize the field of view. For asubstantially greater off-axis angle, the sensor will be outside of theprojected cone of light and no optical gain will be provided. Note thatto provide relatively high optical gain over a substantial field ofview, the collecting area should be quite large compared to the sensor.The area of the aperture should exceed the area of the sensor first byapproximately the ratio of the optical gain, and this ratio should bemultiplied by another large factor to provide a field of view having asolid angle that is much larger than that which would be imaged onto thesensor were it to be placed in the focal plane of the lens.

[0169] While this particular mirror construction has been describedabove as including a spherical or an aspherical lens 609, a Fresnel lensmay replace the plano-convex lens depicted. Additionally, since forlarge fields of views the light rays must be redirected through evenlarger angles, totally internally reflecting (TIR) lenses or reflectorsmay be used and provide additional advantages. If, for example, apartially transmissive reflecting layer 607 with 20 percent transmissionis chosen and an optical gain of 10 is used, the optical gain more thanrecovers the loss incurred in passing through partially transmissivereflector 607. Furthermore, no unsightly or expensive-to-produceaperture window needs to be provided for the sensor and control benefitsof viewing through the layer are also realized.

[0170] In configurations where the viewing angle needs to be large inone direction but relatively small in another, a cylindrical lens may beused. For example, to sense lights from vehicles in adjacent lanes, theviewing angle must be relatively large in the horizontal direction andthe viewing field may be relatively narrow in the vertical direction. Inthis case, lens 609 may be replaced by a cylindrical lens with ahorizontal axis. A stripe of light rather than a circle is projected,and since light gathering takes place in one rather than two directions,the benefit of the squaring effect for the relative areas of the lensaperture in the area of the projected light pattern in the plane of thesensor is lost. Optical gains of 5, for example, are still feasible,however. Composite lenses containing a patchwork of different elementsincluding, for example, sections of aspheric lenses with differentcenter positions and/or focal lengths, or even combinations of differentkinds of elements such as aspheric and cylindrical lenses may be used toretain reasonable optical gain and characterize the field of view. A rowof lens sections with stepped focal center points can serve well towiden the field of view in selected directions while maintaining a goodoverall optical gain. Some amount of diffusion is preferable in all thedesigns to prevent severe irregularity in the sensed light level due tosevere localized irregularities in the projected light pattern that areoften present. The extremely small area sensor will not average theseirregularities to any useful degree. Some lens designs may optionally becemented to the back of the mirror element.

[0171] In each of the constructions described above with respect toFIGS. 10 and 11, any of the mirror constructions described above withrespect to FIGS. 7A-7G may be employed for use as the electrochromicmirror (depicted as layers 607 and 608 in FIG. 11).

[0172]FIG. 12 shows an outside rearview mirror assembly 200 constructedin accordance with another embodiment of the present invention. Outsiderearview mirror assembly 200 includes a mirror 210, which is preferablyan electrochromic mirror, an external mirror housing 212 having amounting portion 214 for mounting mirror assembly 200 to the exterior ofa vehicle, and a signal light 220 mounted behind mirror 210. To enablethe light from signal light 220 to project through electrochromic mirror210, a plurality of signal light areas 222 are formed in theelectrode/reflector of mirror 210 that include window regions containingelectrically conductive material that is at least partially transmissivesimilar to the information display and glare sensor window areasdescribed above with respect to the other embodiments of the presentinvention. Electrochromic mirror 210 may further include a sensor area224 disposed within the reflective coating on electrochromic mirror 210and similarly include window regions containing electrically conductivematerial that is at least partially transmissive so as to allow some ofthe incident light to reach a sensor mounted behind sensor area 224.Alternatively, sensor 224 could be used to sense glare in night drivingconditions and control the dimming of the exterior mirror independentlyor verify that the mirrors are being sufficiently dimmed by the controlcircuit in the interior mirror. In such a case, a more sensitive photosensor may be required, such as a CdS sensor.

[0173] Signal light 220 is preferably provided to serve as a turn signallight and is thus selectively actuated in response to a control signalgenerated by a turn signal actuator 226. The control signal is thereforeapplied to signal light 220 as an intermittent voltage so as to energizesignal light 220 when a driver has actuated the turn signal lever. Asshown in FIG. 15, when vehicle B is in the blind spot of vehicle A wherethe driver of vehicle A cannot see vehicle B, the driver of vehicle Bcannot see the turn signal on the rear of vehicle A. Thus, if the driverof vehicle A activates the turn signal and attempts to change laneswhile vehicle B is in a blind spot, the driver of vehicle B may notreceive any advance notice of the impending lane change, and hence, maynot be able to avoid an accident. By providing a turn signal light in anoutside rearview mirror assembly 200 of vehicle A, the driver of anapproaching vehicle B will be able to see that the driver of vehicle Ais about to change lanes and may thus take appropriate action morequickly so as to avoid an accident. As illustrated in FIG. 15 anddescribed in more detail below, the signal light is preferably mountedwithin mirror assembly at an angle to the mirror surface to project thelight from the signal light outward into the adjacent lanes in the blindspot areas proximate the vehicle.

[0174] Referring again to FIG. 12, electrochromic mirror 220 may becontrolled in a conventional manner by a mirror control circuit 230provided in the inside rearview mirror assembly. Inside mirror controlcircuit 230 receives signals from an ambient light sensor 232, which istypically mounted in a forward facing position on the interior rearviewmirror housing. Control circuit 230 also receives a signal from a glaresensor 234 mounted in a rearward facing position of the interiorrearview mirror assembly. Inside mirror control circuit 230 applies acontrol voltage on a pair of lines 236 in a conventional manner, suchthat a variable voltage is applied essentially across the entire surfaceof electrochromic mirror 210. Thus, by varying the voltage applied tolines 236, control circuit 230 may vary the transmittance of theelectrochromic medium in mirror 210 in response to the light levelssensed by ambient sensor 232 and glare sensor 234. As will be explainedfurther below, an optional third control line 238 may be connectedbetween the inside mirror control circuit 230 and a variable attenuator260 provided in outside mirror assembly 200, so as to selectivelyattenuate the energizing signal applied on lines 228 from turn signalactuator 226 to the signal light 220 in response to the control signalsent on line 238. In this manner, inside mirror control circuit 230 mayselectively and remotely control the intensity of signal light 220 basedupon information obtained from sensors 232 and 234 and thereby eliminatethe need for a sensor to be mounted in each mirror assembly as well asthe associated sensor area 224.

[0175] Mirror assembly 200 may further include an electric heater (notshown) provided behind mirror 210 that is selectively actuated by aheater control circuit 240 via lines 242. Such heaters are known in theart to be effective for deicing and defogging such external rearviewmirrors. Mirror assembly 200 may optionally include a mirror positionservomotor (not shown) that is driven by a mirror position controller244 via lines 246. Such mirror position servomotors and controls arealso known in the art. As will be appreciated by those skilled in theart, mirror assembly 200 may include additional features and elements asare now known in the art or may become known in the future withoutdeparting from the spirit and scope of the present invention.

[0176] An exemplary signal light subassembly 220 is shown in FIG. 13.Such a signal light 220 is disclosed in U.S. Pat. Nos. 5,361,190 and5,788,357, which disclose the signal light in combination with dichroicexterior rearview mirrors that are not electrochromic. The disclosuresof the signal light assembly in U.S. Pat. Nos. 5,361,190 and 5,788,357is incorporated herein by reference. As explained below, however, thesame signal light subassembly may be used in connection with anelectrochromic mirror as may modified versions of the signal lightsubassembly shown in FIG. 13.

[0177] As shown in FIG. 13, signal light 220 includes a printed circuitboard 250 that, in turn, is mounted within a housing 252 having aperipheral edge that serves as a shroud (see FIGS. 6A and 6B) to blockany stray light from exiting the signal light assembly. Signal light 220preferably includes a plurality of LEDs 254 that are mounted to circuitboard 250. LEDs 254 may be mounted in any pattern, but are preferablymounted in a pattern likely to suggest to other vehicle operators thatthe vehicle having such signal mirrors is about to turn. LEDs 254 may beLEDs that emit red or amber light or any other color light as may provedesirable. LEDs 254 are also preferably mounted to circuit board 250 atan angle away from the direction of the driver. By angling LEDs relativeto mirror 210, the light projected from LEDs 254 may be projectedoutward away from the driver towards the area C in which the driver ofanother vehicle would be more likely to notice the signal light, asshown in FIG. 15. Hence, the potential glare from the signal light asviewed by the driver may be effectively reduced.

[0178] Signal light 220 may optionally include a day/night sensor 256also mounted to circuit board 250. If sensor 256 is mounted on circuitboard 250, a shroud 257 is also preferably mounted to shield sensor 256from the light generated by LEDs 254. Also, if sensor 256 is provided insignal light 220, a day/night sensing circuit 258 may also be mounted oncircuit board 250 so as to vary the intensity of LEDs 254 in response tothe detection of the presence or absence of daylight by sensor 256.Thus, if sensor 256 detects daylight, circuit 258 increases theintensity of the light emitted from LEDs 254 to their highest level anddecreases the intensity of the emitted light when sensor 256 detectsthat it is nighttime. The above-noted signal light disclosed in U.S.Pat. Nos. 5,361,190 and 5,788,357 includes such a day/night sensor 256and associated control circuit 258, and therefore, further descriptionof the operation of the signal light in this regard will not beprovided.

[0179] As an alternative to providing a day/night sensor 256 in each ofthe vehicle's exterior rearview mirrors, a variable attenuator 260 orother similar circuit may be provided to vary the driving voltageapplied from the turn signal actuator 226 on line 228 in response to acontrol signal delivered from inside mirror control circuit 230 on adedicated line 238. In this manner, inside mirror control circuit 230may utilize the information provided from ambient light sensor 232 aswell as the information from glare sensor 234 to control the intensityof the light emitted from LEDs 254 and signal light 220. Since theambient light and glare sensors 232 and 234 are already provided in aninternal electrochromic rearview mirror, providing for such remotecontrol by the inside mirror control circuit 230 eliminates the need forproviding additional expensive sensors 256 in the signal light 220 ofeach exterior mirror assembly. As an alternative to running a separatewire 258 to each of the outside rearview mirrors, variable attenuator260 may be provided in the dashboard proximate the turn signal actuatoror otherwise built into the turn signal actuator, such that a singlecontrol line 238 may be wired from inside mirror control circuit 230 tothe turn signal actuator as shown in FIG. 12.

[0180] The intensity of the light emitted from the LEDs may thus bevaried as a function of the light level sensed by ambient sensor 232 orglare sensor 234, or as a function of the light levels sensed by bothsensors 232 and 234. Preferably, LEDs 254 are controlled to be at theirgreatest intensity when ambient sensor 232 detects daylight and at alesser intensity when sensor 232 detects no daylight. Because thetransmittance of the electrochromic medium is decreased when excessiveglare is detected using glare detector 234, the intensity of LEDs 254 ispreferably correspondingly increased so as to maintain a relativelyconstant intensity at nighttime.

[0181] Electrochromic mirror 210 may be constructed in accordance withany of the alternative arrangements disclosed in FIGS. 7A-7F above,where light source 170 represents one of LEDs 254 of signal lightsubassembly 220. Accordingly, each possible combination of the variousconstructions shown in FIGS. 7A-7F with signal light subassembly 220 arenot illustrated or described in further detail. As but one example,however, FIG. 14 shows the manner in which a signal light subassembly220 could be mounted behind a preferred construction that is otherwiseidentical to that shown in FIG. 7C. As apparent from a comparison ofFIG. 7C and FIG. 14, each of signal light areas 222 corresponds towindow 146 of FIG. 7C. As discussed above, for an outside rearviewmirror the reflectance of reflector/electrode 120 is preferably at least35 percent and the transmittance is preferably at least 20 percent so asto meet the minimum reflectance requirements and yet allow sufficienttransmittance so that the light emitted from signal light 220 may bereadily noticed by the driver of an approaching vehicle.

[0182]FIG. 16 shows a front elevational view schematically illustratingan inside mirror assembly 310 according to an alternative embodiment ofthe present invention. Inside mirror assembly 310 may incorporatelight-sensing electronic circuitry of the type illustrated and describedin the above-referenced Canadian Patent No. 1,300,945, U.S. Pat. No.5,204,778, or U.S. Pat. No. 5,451,822, and other circuits capable ofsensing glare and ambient light and supplying a drive voltage to theelectrochromic element.

[0183] Rearview mirrors embodying the present invention preferablyinclude a bezel 344, which conceals and protects the spring clips (notshown) and the peripheral edge portions of the sealing member and boththe front and rear glass elements (described in detail below). Widevarieties of bezel designs are well known in the art, such as, forexample, the bezel disclosed in above-referenced U.S. Pat. No.5,448,397. There is also a wide variety of known housings for attachingthe mirror assembly 310 to the inside front windshield of an automobile;a preferred housing is disclosed in above-referenced U.S. Pat. No.5,337,948.

[0184] The electrical circuit preferably incorporates an ambient lightsensor (not shown) and a glare light sensor 360, the glare light sensorbeing capable of sensing glare light and being typically positionedbehind the glass elements and looking through a section of the mirrorwith the reflective material partially removed in accordance with thisparticular embodiment of the present invention. Alternatively, the glarelight sensor can be positioned outside the reflective surfaces, e.g., inthe bezel 344. Additionally, an area or areas of the third surfacereflective electrode, such as 346, may be partially removed inaccordance with the present invention to permit a display, such as acompass, clock, or other indicia, to show through to the driver of thevehicle. The present invention is also applicable to a mirror which usesonly one video chip light sensor to measure both glare and ambient lightand which is further capable of determining the direction of glare. Anautomatic mirror on the inside of a vehicle, constructed according tothis invention, can also control one or both outside mirrors as slavesin an automatic mirror system.

[0185]FIG. 17 shows a cross-sectional view of mirror assembly 310 alongthe line 17-17′. Like the above-described embodiments, mirror 310 has afront transparent element 112 having a front surface 112 a and a rearsurface 112 b, and a rear element 114 having a front surface 114 a and arear surface 114 b. Since some of the layers of the mirror are verythin, the scale has been distorted for pictorial clarity. A layer of atransparent electrically conductive material 128 is deposited on thesecond surface 112 b to act as an electrode. Transparent conductivematerial 128 may be any of the materials identified above for the otherembodiments. If desired, an optional layer or layers of a colorsuppression material 130 may be deposited between transparent conductivematerial 128 and front glass rear surface 112 b to suppress thereflection of any unwanted portion of the electromagnetic spectrum. Atleast one layer of a material that acts as both a reflector and aconductive electrode 120 is disposed on third surface 114 a of mirror310. Any of the materials/multi-layer films described above maysimilarly be used for reflector/electrode 120. U.S. Pat. No. 5,818,625entitled “DIMMABLE REARVIEW MIRROR INCORPORATING A THIRD SURFACE METALREFLECTOR” and filed on or about Apr. 2, 1997, describes anotherreflector/electrode 120 in detail. The entire disclosure of this patentis incorporated herein by reference.

[0186] In accordance with this embodiment of the present invention, aportion of conductive reflector/electrode 120 is removed to leave aninformation display area 321 comprised of a non-conducting area 321 a(to view a display) and a conducting area 321 b (to color and clear theelectrochromic medium), as shown in FIG. 17. Although only shown indetail for the display area 321, the same design may be, and preferablyis, used for the glare sensor area (160 in FIG. 16). FIG. 18 shows afront elevational view illustrating information display area 321. Again,since some of the layers of this area are very thin, the scales of thefigures have been distorted for pictorial clarity. The portion ofconductive reflector/electrode that is removed 321 a is substantiallydevoid of conductive material, and the portion not removed should be inelectrical contact with the remaining area of reflector/electrode 120.That is to say, there are little or no isolated areas or islands ofreflector/electrode 120 that are not electrically connected to theremaining portions of the reflector/electrode 120. Also, although theetched areas 321 a are shown as U-shaped (FIG. 17), they may have anyshape that allows sufficient current flow through lines 321 b whileallowing the driver to view and read the display 170 through etchedareas 321 a. The reflector/electrode 120 may be removed by varyingtechniques, such as, for example, by etching (laser, chemical, orotherwise), masking during deposition, mechanical scraping,sandblasting, or otherwise. Laser etching is the presently preferredmethod because of its accuracy, speed, and control.

[0187] The information display area 321 is aligned with a display device170 such as a vacuum fluorescent display, cathode ray tube, liquidcrystal, flat panel display and the like, with vacuum fluorescentdisplay being presently preferred. The display 170, having associatedcontrol electronics, may exhibit any information helpful to a vehicleoccupant, such as a compass, clock, or other indicia, such that thedisplay will show through the removed portion 321 a to the vehicleoccupant.

[0188] The area that is substantially devoid of conductivereflector/electrode 321 a and the area having conductivereflector/electrode present 321 b may be in any shape or form so long asthere is sufficient area having conductive material to allow propercoloring and clearing (i.e., reversibly vary the transmittance) of theelectrochromic medium, while at the same time having sufficient areasubstantially devoid of conductive material to allow proper viewing ofthe display device 170. As a general rule, information display area 321should have approximately 70-80 percent of its area substantially devoidof conductive material 321 a and the conductive material 321 b fillingthe remaining 20-30 percent. The areas (321 a and 321 b) may have avariety of patterns such as, for example, linear, circular, elliptical,etc. Also, the demarcation between the reflective regions and theregions devoid of reflective material may be less pronounced by varyingthe thickness of the reflective materials or by selecting a pattern thathas a varying density of reflective material. It is presently preferredthat areas 321 a and 321 b form alternating and contiguous lines (seeFIG. 17). By way of example, and not to be construed in any way aslimiting the scope of the present invention, the lines 321 b generallymay be approximately 0.002 inch wide and spaced approximately 0.006 inchapart from one another by the lines substantially devoid of conductivematerial. It should be understood that although the figures show thelines to be vertical (as viewed by the driver), they may be horizontalor at some angle from vertical. Further, lines 321 a need not bestraight, although straight vertical lines are presently preferred.

[0189] If all of the third surface reflector/electrode 120 is removed inthe information display area 321 or in the area aligned with the glarelight sensor 160, there will be significant coloration variationsbetween those areas and the remaining portion of the mirror where thereflector/electrode 120 is not removed. This is because for everyelectrochromic material oxidized at one electrode there is acorresponding electrochromic material reduced at the other electrode.The oxidation or reduction (depending on the polarity of the electrodes)that occurs on the second surface directly across from the informationdisplay area 321 will occur uniformly across the area of the informationdisplay area. The corresponding electrochemistry on the third surfacewill not, however, be uniform. The generation of light-absorbing specieswill be concentrated at the edges of the information display area (whichis devoid of reflector/electrode). Thus, in the information display area321, the generation of the light-absorbing species at the second surfacewill be uniformly distributed, whereas the light-absorbing species atthe third surface will not, thereby creating aesthetically unappealingcolor discrepancies to the vehicle occupants. By providing lines ofreflector/electrode 120 areas throughout the information display area321, in accordance with the present invention, the generation oflight-absorbing species (at the second and third surfaces) in theinformation display area will be much closer to the uniformity seen inother areas of the mirror with completely balanced electrodes.

[0190] Although those skilled in the art will understand that manymodifications may be made, the laser etching may be accomplished byusing a 50 watt Nd:YAG laser, such as that made by XCEL Control Laser,located in Orlando, Fla. In addition, those skilled in the art willrealize that the power settings, the laser aperture, the mode of thelaser (continuous wave or pulsed wave), the speed with which the lasermoves across the surface, and the wave form of the laser may be adjustedto suit a particular need. In commercially available lasers, there arevarious wave forms that the laser follows while it ablates the surfacecoatings. These wave forms include straight lines, sine waves at variousfrequencies and ramp waves at various frequencies, although many othersmay be used. In the presently preferred embodiments of the presentinvention, the areas devoid of reflective material 321 a are removed byusing the laser in a pulsed wave mode with a frequency of about 3 kHz,having a narrow (e.g., around 0.005 inch) beam width where the laser ismoved in a straight line wave form.

[0191]FIGS. 14B and 14C show two alternate arrangements for implementingthe present invention. FIGS. 14B and 14C are partial cross-sectionalviews taken along lines 14-14′ of FIG. 12. FIG. 14B shows an arrangementsimilar to that of the inside rearview mirror shown in FIG. 17 in whichparallel lines of reflector/electrode material 222 b are provided acrossthe signal light area 222 by either etching out or masking lines 222 ain regions that are devoid of the reflector/electrode material. Each ofthe signal light areas 222 is provided in a position on the rearviewmirror corresponding and overlying one of LEDs 254 as apparent from acomparison of FIGS. 12 and 13. Electrochromic mirror 410 may beconstructed in the same manner as described above for the insiderearview mirror 310 of the preceding embodiment. Specifically, mirror410 includes a front transparent element 112 having a front surface anda rear surface, and a rear element 114 having a front surface 114 a anda rear surface 114 b. Mirror 410 also includes a layer 128 of atransparent conductive material deposited on the rear surface of frontelement 112 or on an optional color suppression material 130 that isdeposited on the rear surface of front element 112. Additionally, mirror410 includes at least one layer 120 disposed on a front surface 114 a ofrear element 314 that acts as both a reflector and a conductiveelectrode. An electrochromic medium is disposed in a chamber definedbetween layers 128 and 120. All of the component elements of mirror 410may be made using the same materials and applied using the sametechniques as described above with respect to the preceding embodiments.Preferably, however, the reflector/electrode material of layer 120 ismade using nickel, chrome, rhodium, stainless steel, silver, silveralloys, platinum, palladium, gold, or combinations thereof.

[0192] The reflectance of the mirror in the signal light areas 222 orsensor area 224 may also be controlled by varying the percentage ofthose areas that are devoid of reflective material or by varying thethickness of the reflector/electrode coating. Further, thereflector/electrode material used to form lines 222 b in signal lightarea may be different from the reflector/electrode material used for theremainder of the mirror. For example, a reflector/electrode materialhaving a higher reflectance may be used in the signal light area suchthat the reflectivity in the signal light area is the same as that ofthe remainder of the mirror despite the regions therein that are devoidof reflector material. Preferably, the region of the signal light areathat is devoid of reflective material constitutes between 30 and 50percent of the signal light area and the area occupied by the reflectivematerial is between 50 and 70 percent of the signal light area. Toachieve these percentages, the lines of reflector/electrode material arepreferably about 0.010 inch wide and the spaces between the lines areabout 0.006 inch wide.

[0193] The arrangement shown in FIG. 14C differs from that shown in FIG.14B in that the reflective material is formed on the fourth surface(i.e., the rear surface 114 b of rear element 114). With such anarrangement, the electrode 340 on the third surface is preferably madeof a transparent material similar to that of the electrode 128 formed onthe rear surface of front element 112. Like the arrangement shown inFIG. 14B, the structure shown in FIG. 14C includes a signal light area222 having alternating regions of reflective material 222 b and regionsdevoid of such reflective material 222 a. In this manner, LEDs 254 maybe more covertly hidden from view by the driver and yet light from LEDs254 may project through all the layers of electrochromic mirror 410 soas to be visible by drivers of other vehicles. Similarly, if a day/nightsensor 256 is provided, a sensor area 224 may be provided in the samemanner with alternating regions of reflective material 224 b and regionsthat are void of reflective material 224 a.

[0194] A benefit of utilizing the above-described structure inconnection with a signal light is that the use of a dichroic coating maybe avoided. Dichroic coatings are generally nonconductive and thereforecannot be used in an electrochromic mirror having a third surfacereflector. Also, the only current dichroic coatings that areeconomically feasible are those that transmit red and infrared light andreflect other colors of light. Thus, to construct a practical signallight, only LEDs that emit red light may be utilized. Accordingly, thereis little flexibility in this regard when a dichroic coating isutilized. To the contrary, with the structure of the present invention,any color signal light may be used.

[0195] The concept of providing a window region having alternating areasdevoid of reflective material may similarly be applied to anon-electrochromic signal mirror. However, although other materials maybe used, chromium on the first or second surface of such anon-electrochromic mirror is the presently preferred reflectivematerial.

[0196]FIGS. 14D and 19 show yet another embodiment of the presentinvention as it pertains to signal mirrors. According to thisembodiment, the signal mirror includes an additional structure forrendering the signal light more covert with respect to the field of viewof the driver. While each of the embodiments relating to the signalmirrors discussed above covertly hides the signal light behind themirror when they are not energized and generally hides the signal lightwhen activated, there remains the possibility with such embodiments thatthe driver may be distracted during the periods in which the signallight is activated. Specifically, while the LEDs of the signal light areangled outward away from the driver's eyes, the driver may still be ableto see the LEDs as points of light through portions of the mirrorassembly. Accordingly, this embodiment provides means for reducing thetransmission of light from the signal light through the mirror in thedirection of the driver. As explained below, this additional means maytake on several alternative or additive forms.

[0197] Referring to FIG. 14D, a construction is shown whereby a baffleassembly 500 is positioned between signal light assembly 220 and therear surface of mirror assembly 510. The particular baffle assembly 500shown in FIG. 14D includes a forward, upper plate 502 and a rearward,lower plate 504 fixed in spaced and parallel relation by a plurality oflegs 506. As illustrated in FIGS. 14D and 19, lower plate 504 islaterally displaced relative to forward plate 502 in a more outwardposition away from the driver. Lower plate 504 includes a plurality ofapertures 508 corresponding in size and position to each of LEDs 254.Upper plate 502 is disposed relative to aperture 508 and slightly overLEDs 254 so as to block the driver's view of LEDs 254. Upper plate 502includes an aperture 509 through which light may pass so as to reachsensor 256. The spaces between upper plate 502 and lower plate 504 aswell as apertures 508 in lower plate 504 provide a sufficient openingfor light projected from the angled LEDs 254 to be transmitted throughmirror 510 and into region C shown in FIG. 15. Baffle assembly 500, asshown, is preferably made of a black plastic or the like.

[0198] The functionality of baffle assembly 500 may be supplemented oralternatively performed by various other mechanisms designated generallyin FIG. 14D by reference numeral 520. Specifically, element 520 may beany one or a combination of a light control film, a layer of black ordark paint, or a heater element. A light control film, such as thatavailable from the 3M Company under the trade designation LCF-P, may beused, which is a thin plastic film enclosing a plurality of closelyspaced, black colored microlouvers. Such a light control film isdisclosed for use in a conventional signal mirror in U.S. Pat. Nos.5,361,190 and 5,788,357, the disclosures of which are herebyincorporated by reference. As disclosed in those patents, such a lightcontrol film may have a thickness of 0.030 inches, with the microlouversspaced approximately 0.005 inches apart. The microlouvers are typicallyblack and are positioned at various angular positions to provide asuitable viewing angle. Such a light control film permits light fromLEDs 254 to be transmitted at the appropriate viewing angle to reachregion C (FIG. 15). The light control film also serves to block thelight projected from LEDs 254 from travelling outside the appropriateviewing angle in the line of sight of the driver. Thus, unlike thebaffle assembly 500 depicted in FIGS. 14D and 19, such a light controlfilm may be placed completely over and in front of each of LEDs 254.Further, such a light control film could also be made using other formsof optical elements, such as holograms and the like.

[0199] If element 520 is a coating of an opaque paint, such a coatingwould not extend far enough in front of the LEDs to block light fromLEDs 254 to be transmitted through mirror 510 into blind spot area C(FIG. 15). Alternatively, such a coating of paint could extendcompletely in front of LEDs 254, provided it was configured to have someform of louver or equivalent structure formed in its surface in theareas of the intended transmission path of LEDs 254. For example, thethickness of such a paint coating could be controlled to createeffective louvers using screen-printing, molding, stamping, or laserablation. Further, if reflector/electrode 120 is configured in themanner described above with respect to FIGS. 14B and 14C, element 520could be a coating of black paint that has similar bars or stripes inthe areas overlying LEDs 254 while having spacial relations relative tothe bars 222 b of reflector/electrode 120, so as to provide atransmission path at the appropriate angle for vehicles to view thelights when in the vehicle's blindspots, while blocking the light fromthe field of view of the driver. Further, as shown in FIG. 14D, the bars222 b of reflector/electrode 120 may be configured to have varyingwidths that decrease with increasing distance from the driver, so as toreduce peripheral transmittance through area 222 in the direction of thedriver, or may have a less pronounced edge definition, as discussedabove.

[0200] If element 520 is provided using a mirror heating element, theheating element could be provided to extend across the entire fourthsurface of the mirror and have apertures formed in appropriate locationsto allow light emitted from LEDs 254 to be transmitted at theappropriate angle.

[0201] Another mechanism for shielding the driver from light emittedfrom LEDs 254 is to increase the thickness of the reflector/electrode120 in a region 530 corresponding to that of upper plate 502 therebyreducing the transmittance through that portion of reflector/electrode120. Currently, such reflector/electrodes have a transmittance ofapproximately 1-2 percent.

[0202] To sufficiently shield the driver from light transmitted fromLEDs 254, reflector/electrode 120 preferably has a thickness in region530 that reduces the transmittance therethrough to less than 0.5percent, and more preferably to less than 0.1 percent.

[0203] Element 520 may additionally or alternately include variousoptical films, such as a prismatic or Fresnel film or a collimatingoptical element as described in U.S. Pat. No. 5,788,357 so as tocollimate and direct the light emitted from LEDs 254 at the appropriateangle without also transmitting light in the direction of the driver.

[0204] As yet another possible solution, sidewalls 252 of light assembly220 may be extended so as to space LEDs 254 further from the rearsurface of mirror assembly 510, such that sidewalls 252 effectivelyblock any light from LEDs 254 from being transmitted in the direction ofthe driver of the vehicle.

[0205] Although the structure shown in FIG. 14D shows mirror assembly510 as including the reflector/electrode 120 as illustrated in theembodiment shown in FIG. 14B above, mirror assembly 510 could take onany of the other forms discussed above with respect to the embodimentdescribed with respect to FIG. 14A or FIGS. 7A-7G.

[0206] Although the present invention has been described as providing asignal light that is used as a turn signal, it will be appreciated bythose skilled in the art that the signal light could function as anyother form of indicator or signal light. For example, the signal lightcould indicate that a door is ajar so as to warn drivers of approachingvehicles that a vehicle occupant may be about to open a door intooncoming traffic, or the light behind the mirror may be an indicatorlight to indicate that the mirror heaters have been turned on, thatanother vehicle is in a blind spot, that the pressure is low, that aturn signal is on, or that freezing/hazardous conditions exist.

[0207] While the signal light of the present invention has beendescribed above as preferably being made of a plurality of LEDs, thesignal light may nevertheless be made of one or more incandescent lamps,or any other light source, and an appropriately colored filter withoutdeparting from the spirit or scope of the present invention.

[0208] Yet another embodiment of the present invention is shown in FIGS.20-22. In this embodiment, an exterior rearview mirror assembly 700 isprovided having a housing 710 adapted for attachment to the exterior ofa vehicle. Such mirrors are often mounted to the vehicle door 730 or tothe A-pillar of the vehicle. Within housing 710 is a mirror structure720 and a light source 725 mounted behind mirror structure 720. Mirror720 may be constructed in accordance with any of the above-notedembodiments, such that light emitted from light source 725 may beprojected through mirror 720. Mirror 720 may thus have a reflectorhaving a masked window portion in front of light source 725 or may havea region 726 that is at least partially transmissive provided in frontof light source 725. As yet another alternative, the region 726 in frontof light source 725 may have a construction similar to that shown inFIG. 14 or the entire reflector in mirror 720 may be partiallytransmissive. As shown in FIGS. 21 and 22, light source 725 ispreferably mounted such that it projects light onto a region of thevehicle door 730 on which the vehicle door handle 735 and lock mechanism737 are provided. Lock mechanism 737 may be a keyhole or touch pad ascommonly used to enable the vehicle doors to be locked or unlocked.

[0209] Light source 725 may be any type of light source, and ispreferably a white light source. A preferred light source is disclosedin commonly-assigned U.S. Provisional Patent Application No. 60/124,493,entitled “SEMICONDUCTOR RADIATION EMITTER PACKAGE,” filed on Mar. 15,1999, by John K. Roberts, the entire disclosure of which is incorporatedherein by reference.

[0210] Light source 725 may be activated so as to project light inresponse to the same actions to which the interior vehicle lights areturned on and off when providing illuminated entry into the vehicle.Thus, for example, light source 725 may illuminate a portion of door 730when a person depresses the lock or unlock key on a key fob associatedwith the vehicle for remote keyless entry (RKE), when a person attemptsto open the door, or when a person inserts a key into the lock mechanism737. Alternatively, a motion sensor may be provided to activate lightsource 725. Preferably, light source 725 is disabled so as to beincapable of projecting light when the vehicle's ignition has beenturned on.

[0211] By providing such a light source 725 within exterior rearviewmirror housing 710, a light source may be mounted on the vehicle forilluminating the area on the exterior of the vehicle where a vehicleoccupant must contact to enter the vehicle. Such a feature isadvantageous when the vehicle is parked in particularly dark locations.

[0212] While light source 725 has been described as being mounted toproject light at door handle 735, it will be appreciated that lightsource 725 could be mounted so as to project light also onto the groundregion or other areas of the exterior of the vehicle as well as to thedoor handle. This could be accomplished by providing appropriate opticsbetween light source 725 and mirror structure 720. Additional lightsources could also be mounted so as to project light onto these areas.

[0213] The transflective (i.e., partially transmissive partiallyreflective) rearview mirror described above allows the display ofinformation to the driver without removing a portion of the reflectivecoating. This results in a more aesthetically pleasing appearance andallows the mirror to appear as a contiguous reflector when the displayis off. An example of a display particularly suited to this applicationis a compass display.

[0214] Many mirrors are sold each year which have the added feature ofdisplaying the heading of a vehicle using an alpha-numeric VacuumFluorescent Display (VFD) capable of displaying eight compass directions(N, S, E, W, NW, SW, NE, SE). These types of displays are used in manyother applications in motor vehicles such as radios and clocks. Thesedisplays have a glass cover over the phosphor digit segments. When usedwith a transflective mirror, the majority of the light from the VFD isnot transmitted through the mirror but reflected back to the display. Aportion of this reflected light is then reflected off both the top andbottom surfaces of the cover glass of the VFD and back through themirror. These multi-bounce reflections result in ghost or double imagesin the display which are highly undesired. As discussed above, asolution to this problem is to provide an anti-reflection coating on thecover glass of the VFD, however, such an anti-reflection coating adds tothe cost of the display. Other disadvantages of VFD displays are thatthey are expensive and fragile.

[0215] An LED alpha-numeric display is a viable alternative to a vacuumfluorescent display for use in a transflective mirror. As discussedabove, LED displays do not have a specular cover glass and thus do notsuffer from ghost reflection problems. Additionally, the areasurrounding the LEDs can be colored black to further aid in suppressingspurious reflections. LEDs also have the advantage of having extremelyhigh reliability and long life. Segmented alpha-numeric LED displays arecommercially available but are complicated to manufacture and it isdifficult to maintain segment to segment brightness and colorconsistency. Finally, it is also difficult to prevent light from onesegment from bleeding into another segment. LEDs are also only availablein saturated highly monochromatic colors, with the exception of somephosphor-LED combinations, which are currently very expensive. Manyautomotive manufacturers have display color schemes which are more broadspectrum and difficult, if not impossible to match with LEDtechnologies. Most cars manufactured in the United States have a bluedisplay color scheme, which could only be matched with blue LEDs whichare currently very expensive.

[0216] An alternative to a segmented LED or VFD display is describedbelow that overcomes the above problems associated with LEDs and VFDs.While the following description is related to a compass display, theconcepts could readily be extended to a variety of information displays,such as a temperature display and various warning lights. The compassdisplay is used as an example in the preferred embodiment because itbest illustrates the features and advantages of the invention. Also, thefollowing description will concentrate on the use of LEDs as thepreferred light source. However, many other light sources are alsoapplicable, such as incandescent bulbs or new emerging technologies suchas light emitting polymers and organic LEDs. The graphical, rather thanalpha-numerical, nature of this display clearly distinguishes it fromother alpha-numerical displays in a vehicle (such as the clock, etc.).Therefore, it will not look undesirable if this display does not matchthe color scheme of the VFD displays throughout the vehicle, allowingthe use of more efficient and cost effective displays. In fact, thecontrasting colors of the display should contribute to the aesthetics ofthe vehicle interior.

[0217] The display in the preferred embodiment consists of multipleLEDs, a graphical applique masking layer, and a transflective mirror. Afront view of the masking layer is shown in FIGS. 23A and 23B. Thegraphical applique shows eight points of a compass (801-808). Theapplique in FIG. 23A includes all eight directions, however, only one ofthe eight directions, as shown in FIG. 1b, will be lit depending on thedirection of travel. The region of the mirror containing the otherdirections will be reflective and not indicate any content. A centergraphic (809) may be an emblem, such as the globe in FIGS. 23A and 23B,can be added for cosmetic appeal. The globe can be illuminated by an LEDof a color contrasting the color of the direction indicators.

[0218] Various methods of controlling the segments are contemplated. Inthe simplest form, only one of the LEDs behind the eight compassdirection indicators is illuminated at a given time, depending on thedirection of travel. In another scheme, all eight indicators are litdimly and the indicator corresponding to the current direction of travelis lit more brightly than the other eight. In yet another scheme,bicolor LEDs are used and the LED indicator corresponding to the currentdirection of travel is set to a different color than the other eight. Afinal alternative would be to have only the indicator corresponding tothe current direction of travel lit, but gradually fade from oneindicator to another as the car changes directions.

[0219] The construction of the display is described with reference toFIGS. 24 and 25. FIG. 24 shows the arrangement of LEDs on a circuitboard and FIG. 25 shows an exploded view of the display assembly. TheLEDs (812) are arranged on a circuit board (811) in a patterncorresponding to the locations of the indicators and center graphic.LEDs (812) may be of the type trade named “Pixar” by Hewlett Packard.Due to the loss of light in the transflective coating, bright LEDs areneeded. AlInGaP based LEDs are suitable for this application and areavailable in green, red, amber, and various similar colors. Blue andgreen colors can be achieved by using InGaN LEDs. Although InGaN LEDsare currently expensive, there are many fewer LEDs needed than would beused in a segmented display. As an alternative to using packaged LEDssuch as the “Pixar” LED, they can be bonded to the circuit boarddirectly using a technique commonly known in the industry asChip-On-Board.

[0220] The circuit board (811) is positioned behind the mirror usingspacer (813). The spacer (813) serves multiple purposes. First, thespacer positions the circuit board a distance from the mirror, {fraction(1/4)} inch for example, such that the light from the LED fully coversthe indicator. Second, the spacer prevents cross talk between indicatorsby preventing light from one cavity from entering another cavity. Toachieve this, the spacer should be made from a white, highly reflectivematerial. At the least, the spacer must be opaque. Finally, the spacerserves to help reflect light exiting the LED at high angles back towardsthe indicator. This improves the efficiency of the system. The spacermay even be constructed with a parabolic bowl surrounding the LED tomost effectively direct light forward. A lambertian scattering surfaceon the spacer will also help diffuse the light and improve theuniformity of the indicator illumination. The empty region between thecircuit board (811) and the mirror (815) formed by the openings in thespacer (813) may be filled with an epoxy or silicone containing adiffusant. This will help further diffuse the light and help theindicators appear more uniform.

[0221] An applique (814) is provided in a masking layer made of a thinmaterial which has a black matte mask covering all areas but thegraphical indicators. The regions for the graphic are a clear orsomewhat white and diffuse. The applique may be formed by silk-screeningthe black mask pattern onto a film of diffuse plastic. Preferably, theside of the applique facing the LEDs is also screened with a white ink.This will allow light which does not pass through the letters orgraphical region to reflect back onto the LED and spacer where it maythen partially reflect back forward. Alternatively, the applique can beformed by directly silk screening the black mask onto the back surfaceof mirror (815). The manner by which such an applique may be constructedis disclosed in U.S. Pat. No. 6,170,956, entitled “REARVIEW MIRRORDISPLAY,” filed on May 13, 1999, by Wayne J. Rumsey et al, the entiredisclosure of which is herein incorporated by reference.

[0222] While the invention has been described in detail herein inaccordance with certain preferred embodiments thereof, manymodifications and changes therein may be effected by those skilled inthe art without departing from the spirit of the invention. Accordingly,it is our intent to be limited only by the scope of the appending claimsand not by way of the details and instrumentalities describing theembodiments shown herein.

The invention claimed is:
 1. An electrochromic rearview mirrorcomprising: front and rear elements each having front and rear surfacesand being sealably bonded together in a spaced-apart relationship todefine a chamber; a transparent first electrode including a layer ofconductive material carried on a surface of one of said elements; anelectrochromic material contained in said chamber; and a partiallytransmissive, partially reflective second electrode disposed oversubstantially all of said front surface of said rear element, saidsecond electrode including a transparent coating applied over a surfaceof said rear element and a thin reflective layer of metal applied oversaid transparent coating, wherein said electrochromic rearview mirrorexhibits a reflectance of at least about 35 percent, a transmittance ofat least about 5 percent in at least portions of the visible spectrum,and a C* value of less than about 20.